Ramana Sri IAS

2021 IFoS Maths Optional Paper II Solutions
2021 IFoS Maths Optional Paper II Solutions

2021 IFoS Maths Optional Paper II Solutions

Ramana Sri IAS provides complete and updated solutions for the 2021 IFoS Maths Optional Paper II. Aspirants preparing for the IFoS Mains Examination with Mathematics as their optional subject should solve all these questions carefully before the mains examination.

Ramana Sri IAS presents complete solutions for Indian Forest Service Examination 2021 Mathematics Optional Paper II. Each answer follows the same format: Question, Diagram where needed, Concept Related to the Question, Detailed Solution, and Final Answer.

About 2021 IFoS Maths Optional Paper II Solutions

These 2021 IFoS Maths Optional Paper II Solutions are prepared by Ramana Sri IAS for aspirants who want question-wise clarity before the IFoS Mains examination. This public page gives one full sample solution, while the complete paper-wise solutions are available in the full PYQ course.

Students can use these 2021 IFoS Maths Optional Paper II Solutions to understand the expected answer-writing method, diagram presentation, concept application, and final-answer format used by Ramana Sri IAS.

For the official examination source, students may also refer to the UPSC previous year question papers page.

These 2021 IFoS Maths Optional Paper II Solutions are useful for revision, answer-writing practice, and understanding the step-by-step method expected in the IFoS Mathematics optional paper.

Sample Full Solution

We are giving one question from 2021 IFoS Maths Optional Paper II Solutions as a free sample solution below: Question 1(c). This free sample includes all five sections: Question, Diagram, Concept Related to the Question, Detailed Solution, and Final Answer. Complete 2021 IFoS Maths Optional Paper II Solutions for all questions are available in the full PYQ course. To purchase the full solution, please fill out the admission form first. Our Ramana Sri IAS admission team will guide you through WhatsApp, email, or call.

Question 1(a)

Group Theory – Power Automorphism

1Question

Let \(G\) be a finite commutative group. Let \(n\in\mathbb Z\) be such that \(n\) and the order of \(G\) are relatively prime. Show that the function \(\phi:G\to G\) defined by \(\phi(a)=a^n\), for all \(a\in G\), is an isomorphism of \(G\) onto \(G\).

2Diagram

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The Diagram section for this question is available in the full 2021 IFoS Maths Optional Paper II PYQ Solutions course.

Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

3Concept Related to the Question

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The Concept Related to the Question section for this question is available in the full 2021 IFoS Maths Optional Paper II PYQ Solutions course.

Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

4Detailed Solution

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The Detailed Solution section for this question is available in the full 2021 IFoS Maths Optional Paper II PYQ Solutions course.

Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

5Final Answer

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The Final Answer section for this question is available in the full 2021 IFoS Maths Optional Paper II PYQ Solutions course.

Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

Question 1(b)

Real Analysis – Cauchy Criterion

1Question

Apply Cauchy's Principle of Convergence to prove that the sequence \(\langle f_n\rangle\) defined by \(f_n=1+\frac14+\frac17+\cdots+\frac1{3n-2}\) is not convergent.

2Diagram

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The Diagram section for this question is available in the full 2021 IFoS Maths Optional Paper II PYQ Solutions course.

Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

3Concept Related to the Question

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The Concept Related to the Question section for this question is available in the full 2021 IFoS Maths Optional Paper II PYQ Solutions course.

Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

4Detailed Solution

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The Detailed Solution section for this question is available in the full 2021 IFoS Maths Optional Paper II PYQ Solutions course.

Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

5Final Answer

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

Question 1(c)

Implicit Differentiation

1Question

Find \(\frac{dy}{dx}\), when \(f(x,y)=\log(x^2+y^2)+\tan^{-1}\left(\frac yx\right)=0\), on using derivatives of implicit functions.

2Diagram

Question 1(c): Implicit Curve as Logarithmic Spiral
2021 IFoS Maths Optional Paper II Solutions diagram showing the implicit curve as a logarithmic spiral in polar form with axes, origin, and equation labels for visual understanding.

3Concept Related to the Question

For an implicit equation \(F(x,y)=0\), the derivative is \(\frac{dy}{dx}=-\frac{F_x}{F_y}\), provided \(F_y\ne0\).

4Detailed Solution

Let \(F(x,y)=\log(x^2+y^2)+\tan^{-1}(y/x)\). Then \(F_x=\frac{2x}{x^2+y^2}-\frac{y}{x^2+y^2}=\frac{2x-y}{x^2+y^2}\).

Also \(F_y=\frac{2y}{x^2+y^2}+\frac{x}{x^2+y^2}=\frac{x+2y}{x^2+y^2}\). Therefore \(\frac{dy}{dx}=-\frac{F_x}{F_y}=-\frac{2x-y}{x+2y}=\frac{y-2x}{x+2y}\).

5Final Answer

\(\displaystyle \frac{dy}{dx}=\frac{y-2x}{x+2y}\).

Question 1(d)

Assignment Problem – LPP Formulation

1Question

An automobile dealer wishes to put four repairmen \(R_1,R_2,R_3,R_4\) to four different jobs \(J_1,J_2,J_3,J_4\). But \(R_3\) cannot do the job \(J_2\). The estimated man-hours are:

JobR1R2R3R4
J16234
J2975
J36475
J46889

Formulate the above as a Linear Programming Problem.

2Diagram

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

3Concept Related to the Question

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

4Detailed Solution

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

5Final Answer

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

Question 1(e)

Complex Analysis – Analytic Functions

1Question

If \(f(z)=u+iv\) is any analytic function of the complex variable \(z\) and \(u-v=e^x(\cos y-\sin y)\), find \(f(z)\) in terms of \(z\).

2Diagram

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

3Concept Related to the Question

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

4Detailed Solution

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The Detailed Solution section for this question is available in the full 2021 IFoS Maths Optional Paper II PYQ Solutions course.

Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

5Final Answer

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

Question 2(a)

Group Theory – Cayley Theorem

1Question

Prove that every group is isomorphic to a permutation group.

2Diagram

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

3Concept Related to the Question

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

4Detailed Solution

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

5Final Answer

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

Question 2(b)

Improper Integrals

1Question

Examine the convergence of \(\displaystyle \int_0^\infty\frac{dx}{(1+x)\sqrt{x}}\) and find its value, if possible.

2Diagram

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

3Concept Related to the Question

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

4Detailed Solution

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

5Final Answer

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

Question 2(c)

Complex Analysis – Taylor Series

1Question

Find the Taylor's series expansion of the function of the complex variable \(f(z)=\frac1{(z-1)(z-3)}\) about the point \(z=4\). Find its radius of convergence.

2Diagram

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

3Concept Related to the Question

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

4Detailed Solution

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The Detailed Solution section for this question is available in the full 2021 IFoS Maths Optional Paper II PYQ Solutions course.

Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

5Final Answer

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

Question 3(a)

Functions of Two Variables – Maxima and Minima

1Question

Examine the existence of maxima and minima of the function \(u(x,y)=xy+\frac8x+\frac8y\).

2Diagram

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

3Concept Related to the Question

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

4Detailed Solution

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The Detailed Solution section for this question is available in the full 2021 IFoS Maths Optional Paper II PYQ Solutions course.

Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

5Final Answer

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

Question 3(b)

Ring Theory – Prime Ideals and Boolean Rings

1Question

(i) Let \(R\) be a non-zero commutative ring with unity. If every ideal of \(R\) is prime, prove that \(R\) is a field.

(ii) Let \(R\) be a commutative ring with unity such that \(a^2=a\), for all \(a\in R\). If \(I\) is any prime ideal of \(R\), find all the elements of \(R/I\).

2Diagram

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

3Concept Related to the Question

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

4Detailed Solution

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The Detailed Solution section for this question is available in the full 2021 IFoS Maths Optional Paper II PYQ Solutions course.

Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

5Final Answer

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

Question 3(c)

Linear Programming – Duality

1Question

Consider the following Linear Programming Problem as primal: minimize \(z=30x_1+20x_2\), subject to \(3x_1+5x_2\ge100\), \(2x_1+x_2\ge120\), \(5x_1+3x_2\ge90\), \(x_1,x_2\ge0\). Then, using the principle of duality, find the optimal solution of the primal.

2Diagram

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

3Concept Related to the Question

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The Concept Related to the Question section for this question is available in the full 2021 IFoS Maths Optional Paper II PYQ Solutions course.

Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

4Detailed Solution

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The Detailed Solution section for this question is available in the full 2021 IFoS Maths Optional Paper II PYQ Solutions course.

Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

5Final Answer

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The Final Answer section for this question is available in the full 2021 IFoS Maths Optional Paper II PYQ Solutions course.

Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

Question 4(a)

Complex Analysis – Definite Integral

1Question

Show that \(\displaystyle \int_0^{2\pi}\frac{\cos3\theta}{5-4\cos\theta}\,d\theta=\frac\pi{12}\).

2Diagram

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

3Concept Related to the Question

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

4Detailed Solution

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

5Final Answer

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

Question 4(b)

Algebra – Euclidean Domains

1Question

Show that an element \(x\) in a Euclidean domain is a unit if and only if \(d(x)=d(1)\), where the notations have their usual meanings.

2Diagram

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

3Concept Related to the Question

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

4Detailed Solution

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The Detailed Solution section for this question is available in the full 2021 IFoS Maths Optional Paper II PYQ Solutions course.

Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

5Final Answer

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

Question 4(c)

Operations Research – Transportation Problem

1Question

Starting with Least Cost Method, find all the solutions to the following transportation problem:

Plants/WarehousesIIIIIIIVSupply
A865318
B676820
C1084518
Demand1516121356

2Diagram

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

3Concept Related to the Question

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

4Detailed Solution

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

5Final Answer

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

Question 5(a)

Partial Differential Equations – Complete Primitive

1Question

Find the complete primitive of \(4r-4s+t=16\log_e(x+2y)\), where \(r,s,t\) bear their usual meanings.

2Diagram

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

3Concept Related to the Question

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The Concept Related to the Question section for this question is available in the full 2021 IFoS Maths Optional Paper II PYQ Solutions course.

Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

4Detailed Solution

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The Detailed Solution section for this question is available in the full 2021 IFoS Maths Optional Paper II PYQ Solutions course.

Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

5Final Answer

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

Question 5(b)

Numerical Analysis – Interpolation

1Question

From the following table, estimate the number of students who obtained marks between \(40\) and \(46\):

Marks30–4040–5050–6060–7070–80
No. of students3243554030

2Diagram

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

3Concept Related to the Question

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The Concept Related to the Question section for this question is available in the full 2021 IFoS Maths Optional Paper II PYQ Solutions course.

Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

4Detailed Solution

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The Detailed Solution section for this question is available in the full 2021 IFoS Maths Optional Paper II PYQ Solutions course.

Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

5Final Answer

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The Final Answer section for this question is available in the full 2021 IFoS Maths Optional Paper II PYQ Solutions course.

Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

Question 5(c)

Computer Arithmetic – Bitwise Operations

1Question

Consider the following integers and their 8-bit binary representations: \(13=00001101\), \(20=00010100\). Perform the following bitwise operations and express the results in decimal system: (i) \(13\&20\) (Bitwise AND), (ii) \(13|20\) (Bitwise OR), (iii) \(13\,\hat{}\,20\) (Bitwise XOR), (iv) \(\sim20\) (Bitwise Complement).

2Diagram

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

3Concept Related to the Question

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

4Detailed Solution

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The Detailed Solution section for this question is available in the full 2021 IFoS Maths Optional Paper II PYQ Solutions course.

Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

5Final Answer

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

Question 5(d)

Analytical Mechanics – Particle on Parabolic Wire

1Question

Examine the motion of a particle sliding on a parabolic wire given by \(x^2=2y\).

2Diagram

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3Concept Related to the Question

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

4Detailed Solution

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

5Final Answer

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Question 5(e)

Differential Equations – Orthogonal Trajectories

1Question

Find the orthogonal trajectory of the family of curves \(x^2-y^2=a^2\). Then sketch the two families to demonstrate whether they cut orthogonally.

2Diagram

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3Concept Related to the Question

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4Detailed Solution

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

5Final Answer

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Question 6(a)

Partial Differential Equations – Charpit Method

1Question

Solve the following by Charpit's method: \(pxy+pq+qy=yz\), where \(p=\frac{\partial z}{\partial x}\) and \(q=\frac{\partial z}{\partial y}\).

2Diagram

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3Concept Related to the Question

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

4Detailed Solution

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

5Final Answer

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

Question 6(b)

Numerical Analysis – Regula-Falsi Method

1Question

Using Regula-Falsi method, find the fourth root of \(28\) correct to three decimal places.

2Diagram

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3Concept Related to the Question

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4Detailed Solution

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

5Final Answer

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Question 6(c)

Fluid Dynamics – Possible Motion and Streamlines

1Question

Verify whether the motion given by \(\vec q=(3x\hat i-2y\hat j)xy^2\) is a possible fluid motion. If so, is it of the potential kind? Accordingly find out the streamlines and the velocity potential or the angular velocity if the fluid was replaced by a rigid solid.

2Diagram

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3Concept Related to the Question

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4Detailed Solution

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

5Final Answer

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

Question 7(a)

Numerical Analysis – Runge-Kutta Method

1Question

Write down the algorithm and flowchart of Runge-Kutta method of fourth order to find the numerical solution at \(x=0.8\) for \(\frac{dy}{dx}=\sqrt{2(x+y)}\), \(y(0.4)=0.82\). Assume the step length \(h=0.2\).

2Diagram

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3Concept Related to the Question

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4Detailed Solution

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

5Final Answer

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

Question 7(b)

Fluid Dynamics – Complex Potential

1Question

Discuss the flow given by the complex potential \(w=\log_e\left(z-\frac{a^2}{z}\right)\). Draw sketches of the streamlines and explain the flow directions along the streamlines.

2Diagram

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3Concept Related to the Question

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4Detailed Solution

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5Final Answer

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

Question 7(c)

Partial Differential Equations – Lagrange Method

1Question

Solve the following differential equation: \((y^2+z^2-x^2)p-2xyq+2xz=0\), where \(p=\frac{\partial z}{\partial x}\) and \(q=\frac{\partial z}{\partial y}\).

2Diagram

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3Concept Related to the Question

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4Detailed Solution

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5Final Answer

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Question 8(a)

Analytical Mechanics – Lagrange Equations in Spherical Coordinates

1Question

Derive the Lagrange's equation for a spherical problem.

2Diagram

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3Concept Related to the Question

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4Detailed Solution

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5Final Answer

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Question 8(b)

Numerical Analysis – Gauss-Seidel Method

1Question

Solve the following system of equations by Gauss-Seidel method: \(20x+y-3z=16\), \(2x+20y-z=-19\), \(3x-2y+20z=25\), starting with the initial solution \(x_0=y_0=z_0=0\).

2Diagram

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3Concept Related to the Question

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4Detailed Solution

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

5Final Answer

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Question 8(c)

Differential Equations – Singular Solution

1Question

Find the singular solution of \(yp^2-2xp+y=0\). Also trace the graph.

2Diagram

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3Concept Related to the Question

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

4Detailed Solution

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The Detailed Solution section for this question is available in the full 2021 IFoS Maths Optional Paper II PYQ Solutions course.

Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

5Final Answer

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Complete diagrams, concepts, detailed solutions and final answers for all questions are available in the full PYQ course.

2021 IFoS Maths Optional Paper II Solutions FAQs

Are these 2021 IFoS Maths Optional Paper II Solutions complete?

This public page gives one full sample solution for 2021 IFoS Maths Optional Paper II Solutions. Complete question-wise solutions for the full paper are available in the full PYQ course.

Which question is given as a free sample solution on this page?

Question 1(c) is given as the free sample solution on this 2021 IFoS Maths Optional Paper II Solutions page.

How should I use these 2021 IFoS Maths Optional Paper II Solutions for preparation?

Students should first solve the question independently, then compare their method with the solution format, diagram presentation, concept explanation, detailed solution, and final answer.

Do these solutions include diagrams and detailed solutions?

Yes. The complete PYQ course includes question-wise diagrams where needed, concept related to the question, detailed solutions, and final answers.

How can I get complete solutions for all questions in 2021 IFoS Maths Optional Paper II?

To get complete solutions for all questions, students can fill out the admission form. The Ramana Sri IAS admission team will guide students through WhatsApp, email, or call.

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