Ramana Sri IAS

Ramana Sri IAS - 2021 UPSC Maths Optional Paper II Solutions

2021 UPSC Maths Optional Paper II Solutions

Ramana Sri IAS provides complete and updated solutions for the 2021 UPSC Maths Optional Paper II. Aspirants preparing for the UPSC Mains Examination with Mathematics as their optional subject should solve all these questions carefully at least 5 to 10 times before the mains examination.

Ramana Sri IAS presents complete solutions for UPSC/IAS/CSE-Civil 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 UPSC Maths Optional Paper II Solutions

These 2021 UPSC Maths Optional Paper II Solutions are prepared by Ramana Sri IAS for aspirants who want question-wise clarity before the UPSC 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 UPSC 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 UPSC Maths Optional Paper II Solutions are useful for revision, answer-writing practice, and understanding the step-by-step method expected in the UPSC Mathematics optional paper.

Sample Full Solution

We are giving one question from 2021 UPSC Maths Optional Paper II Solutions as a free sample solution below: Question 1(d). This free sample includes all five sections: Question, Diagram, Concept Related to the Question, Detailed Solution, and Final Answer. Complete 2021 UPSC 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.

2021 UPSC Maths Optional Paper II Solutions: Table of Contents

Question 1(a)

Bezout identity for several integers

1Question

Let \(m_1,m_2,\ldots,m_k\) be positive integers and \(d\gt0\) the greatest common divisor of \(m_1,m_2,\ldots,m_k\). Show that there exist integers \(x_1,x_2,\ldots,x_k\) such that \(d=x_1m_1+x_2m_2+\cdots+x_km_k\).

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 UPSC 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 UPSC 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 UPSC 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)

Uniform convergence of a series

1Question

Test the uniform convergence of the series \(x^4+\frac{x^4}{1+x^4}+\frac{x^4}{(1+x^4)^2}+\frac{x^4}{(1+x^4)^3}+\cdots\) on \([0,1]\).

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 UPSC 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 UPSC 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)

Monotone functions and Riemann integrability

1Question

If a function \(f\) is monotonic in the interval \([a,b]\), then prove that \(f\) is Riemann integrable in \([a,b]\).

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 UPSC 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 UPSC 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(d)

Contour integral on a circle

1Question

Let \(c:[0,1]\to C\) be the curve, where \(c(t)=e^{4\pi it}\), \(0\leq t\leq1\). Evaluate the contour integral \(\int_c\frac{dz}{2z^2-5z+2}\).

2Diagram

Question 1(d): Contour integral on the unit circle
2021 UPSC Maths Optional Paper II Solutions diagram showing the unit circle traversed twice counterclockwise, with the pole at z equals one half inside and the pole at z equals two outside.

3Concept Related to the Question

The curve \(c(t)=e^{4\pi it}\) describes the unit circle twice in the counterclockwise direction. We locate the poles and apply the residue theorem with winding number two.

4Detailed Solution

Factor the denominator:

\[2z^2-5z+2=(2z-1)(z-2).\]

So the poles are

\[z=\frac12,\\qquad z=2.\]

The curve is the unit circle travelled twice counterclockwise. Thus \(z=\frac12\) lies inside the curve and \(z=2\) lies outside.

The residue at \(z=\frac12\) is

\[\operatorname{Res}_{z=1/2}\frac{1}{2z^2-5z+2}=\frac{1}{4(1/2)-5}=-\frac13.\]

Because the circle is traversed twice, the integral is

\[2\cdot2\pi i\left(-\frac13\right)=-\frac{4\pi i}{3}.\]

5Final Answer

The value of the contour integral is \(-\frac{4\pi i}{3}\).

Question 1(e)

Assignment problem

1Question

A department of a company has five employees with five jobs to be performed. The time, in hours, that each man takes to perform each job is given in the effectiveness matrix. Assign all the jobs to these five employees to minimize the total processing time:

JobIIIIIIIVV
A105131516
B3918136
C107222
D7119712
E7910412

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(a)

Maximum and minimum on a closed interval

1Question

Find the maximum and minimum values of \(f(x)=x^3-9x^2+26x-24\) for \(0\leq x\leq1\).

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)

Field extension containing a root

1Question

Let \(F\) be a field and \(f(x)\in F[x]\) a polynomial of degree \(\gt0\) over \(F\). Show that there is a field \(F'\) and an imbedding \(q:F\to F'\) s.t. the polynomial \(f^q\in F'[x]\) has a root in \(F'\), where \(f^q\) is obtained by replacing each coefficient \(a\) of \(f\) by \(q(a)\).

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)

Laurent series about a shifted centre

1Question

Find the Laurent series expansion of \(f(z)=\frac{z^2-z+1}{z(z^2-3z+2)}\) in the powers of \((z+1)\) in the region \(\lvert z+1\rvert\gt3\).

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 3(a)

Essential singularity at the origin

1Question

Let \(f\) be an entire function whose Taylor series expansion with centre \(z=0\) has infinitely many terms. Show that \(z=0\) is an essential singularity of \(f\left(\frac1z\right)\).

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 3(b)

Stationary values with two constraints

1Question

Find the stationary values of \(x^2+y^2+z^2\) subject to the conditions \(ax^2+by^2+cz^2=1\) and \(lx+my+nz=0\). Interpret the result geometrically.

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 3(c)

Dual of a mixed LPP

1Question

Convert the following LPP into dual LPP: Minimize \(Z=x_1-3x_2-2x_3\), subject to \(3x_1-x_2+2x_3\leq7\), \(2x_1-4x_2\geq12\), \(-4x_1+3x_2+8x_3=10\), where \(x_1,x_2\geq0\) and \(x_3\) is unrestricted in sign.

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 UPSC 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(a)

Subgroups of the additive group of rationals

1Question

Show that there are infinitely many subgroups of the additive group \(Q\) of rational numbers.

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 UPSC 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(b)

Contour integral with sine integral

1Question

Using contour integration, evaluate the integral \(\int_{-\infty}^{\infty}\frac{\sin x\,dx}{x(x^2+a^2)}\), \(a\gt0\).

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(c)

Big M method in linear programming

1Question

Solve the following linear programming problem using Big M method: Maximize \(Z=4x_1+5x_2+2x_3\), subject to \(2x_1+x_2+x_3\geq10\), \(x_1+3x_2+x_3\leq12\), \(x_1+x_2+x_3=6\), \(x_1,x_2,x_3\geq0\).

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 UPSC 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(a)

Formation of first order PDE

1Question

Obtain the partial differential equation by eliminating arbitrary function \(f\) from the equation \(f(x+y+z,x^2+y^2+z^2)=0\).

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 UPSC 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)

Newton-Raphson numerical root

1Question

Find a positive root of the equation \(3x=1+\cos x\) by a numerical technique using initial values \(0,\frac{\pi}{2}\), and further improve the result using Newton-Raphson method correct to \(8\) significant figures.

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 UPSC 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 UPSC 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 UPSC 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)(i)

Number system conversion

1Question

Convert \((3798\cdot3875)_{10}\) into octal and hexadecimal equivalents.

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(c)(ii)

Principal conjunctive normal form

1Question

Obtain the principal conjunctive normal form of \((\neg P\to R)\land(Q\Leftrightarrow P)\).

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 5(d)

D’Alembert principle on a circle

1Question

A particle is constrained to move along a circle lying in the vertical \(xy\)-plane. With the help of D’Alembert’s principle, show that its equation of motion is \(x\ddot y-y\ddot x-gx=0\), where \(g\) is the acceleration due to gravity.

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 5(e)

Sources, sinks and streamlines

1Question

What arrangements of sources and sinks can have the velocity potential \(w=\log_e\left(z-\frac{a^2}{z}\right)\)? Draw the corresponding sketch of the streamlines and prove that two of them subdivide into the circle \(r=a\) and the axis of \(y\).

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 6(a)

Wave equation with fixed ends

1Question

Solve the wave equation \(a^2\frac{\partial^2u}{\partial x^2}=\frac{\partial^2u}{\partial t^2}\), \(0\lt x\lt L\), \(t\gt0\), subject to the conditions \(u(0,t)=0\), \(u(L,t)=0\), \(u(x,0)=\frac14x(L-x)\), and \(\frac{\partial u}{\partial t}(x,0)=0\).

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 6(b)

Boolean function and gate network

1Question

Obtain the Boolean function \(F(x,y,z)\) based on the table given below. Then simplify \(F(x,y,z)\) and draw the corresponding GATE network:

xyzF(x,y,z)
1111
1101
1011
1000
0111
0100
0010
0000

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 6(c)

Lagrangian equation for two masses over a pulley

1Question

Obtain the Lagrangian equation for the motion of a system of two particles of unequal masses connected by an inextensible string passing over a small smooth pulley.

2Diagram

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Question 7(a)

Linear PDE with constant coefficients

1Question

Find the general solution of the partial differential equation \((D^2-D'^2-3D+3D')z=xy+e^{x+2y}\), where \(D=\frac{\partial}{\partial x}\) and \(D'=\frac{\partial}{\partial y}\).

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Question 7(b)

Gauss-Seidel method

1Question

Solve the system of equations \(3x_1+9x_2-2x_3=11\), \(4x_1+2x_2+13x_3=24\), \(4x_1-2x_2+x_3=-8\), correct up to \(4\) significant figures by using Gauss-Seidel method after verifying whether the method is applicable in your transformed form of the system.

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Question 7(c)

Incompressible circular flow

1Question

Show that \(\vec q=\frac{\lambda(-y\hat i+x\hat j)}{x^2+y^2}\), where \(\lambda\) is constant, is a possible incompressible fluid motion. Determine the streamlines. Is the kind of motion potential? If yes, then find the velocity potential.

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Question 8(a)

Complete integral by Charpit method

1Question

Find a complete integral of the partial differential equation \(p=(z+qy)^2\) by using Charpit’s method.

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Question 8(b)

Newton backward interpolation formula

1Question

Derive Newton’s backward difference interpolation formula and also do error analysis.

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Question 8(c)

Complex potential and circular streamlines

1Question

Show that for the complex potential \(\tan^{-1}z\), the streamlines and equipotential curves are circles. Find the velocity at any point and check the singularities at \(z=\pm i\).

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2021 UPSC Maths Optional Paper II Solutions FAQs

Are these 2021 UPSC Maths Optional Paper II Solutions complete?

This public page gives one full sample solution for 2021 UPSC 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(d) is given as the free sample solution on this 2021 UPSC Maths Optional Paper II Solutions page.

How should I use these 2021 UPSC 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.

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