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JNTU B.Tech II Year MATHEMATICS - IV Previous Question Paper (April/May-2023 - R18)

B.Tech | II Year | I | R18 | April/May-2023

Answer PaperPaper Code: 153SBMaximum Marks: 75Time: 3 Hours

Note: i) Question paper consists of Part A, Part B.
ii) Part A is compulsory, which carries 25 marks. In Part A, answer all questions.
iii) In Part B, Answer any one question from each unit. Each question carries 10 marks and may have a, b as sub questions.

Part A

1a

Define the limit of a complex function f(z).

2 marks

Answer

A complex function f(z) is said to have a limit L as z approaches z₀, denoted by limz→z₀ f(z) = L, if for every given ε > 0, there exists a δ > 0 such that |f(z) - L| < ε whenever 0 < |z - z₀| < δ.

1b

State Cauchy-Reimann equations in polar form and check the validity C-R equations for the function

f(r, θ) = reiθ
.

3 marks

Answer

The Cauchy-Riemann equations in polar form for a function f(r, θ) = u(r, θ) + iv(r, θ) are given by:

∂u/∂r = (1/r)(∂v/∂θ)
∂v/∂r = -(1/r)(∂u/∂θ)

Given the function f(r, θ) = reiθ, we use Euler's formula eiθ = cos θ + i sin θ to express it as:

f(r, θ) = r(cos θ + i sin θ) = r cos θ + i(r sin θ)

Here, u = r cos θ and v = r sin θ. We calculate the partial derivatives:

  • ∂u/∂r = cos θ
  • ∂u/∂θ = -r sin θ
  • ∂v/∂r = sin θ
  • ∂v/∂θ = r cos θ

Checking the equations:

  • ∂u/∂r = cos θ and (1/r)(∂v/∂θ) = (1/r)(r cos θ) = cos θ. Thus, ∂u/∂r = (1/r)(∂v/∂θ) holds.
  • ∂v/∂r = sin θ and -(1/r)(∂u/∂θ) = -(1/r)(-r sin θ) = sin θ. Thus, ∂v/∂r = -(1/r)(∂u/∂θ) holds.

Since both equations are satisfied, the Cauchy-Riemann equations hold for the given function.

1c

Define the generalized Cauchy’s integral formula.

2 marks

Answer

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1d

Define an isolated singularity and essential singularity and give one example for each.

3 marks

Answer

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1e

Explain the process of evaluating an improper integral.

2 marks

Answer

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1f

Write the properties of the bilinear transformation.

3 marks

Answer

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1g

Write the Dirichlet’s conditions for the existance of Fourier transform.

2 marks

Answer

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1h

Define Fourier sine and cosine integrals.

3 marks

Answer

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1i

Classify the partial differential equation

∂2u/∂x2 + ∂2u/∂y2 + 5u = 0
.

2 marks

Answer

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1j

Find one independent solution of

∂3z/∂x3 + ∂2z/∂y2 = 0
by method of separation of variables.

3 marks

Answer

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Part B

210 marks
a

Show that the function f(z) = xy is not analytic at the origin even though CR equations are satisfied.

5 marks

Answer

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b

Determine the analytic function whose real part is

ex(x cos 2y - y sin 2y)
.

5 marks

Answer

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OR
310 marks
a

If f(z) is a regular function of z, prove that

∂2|f(z)|2/∂x2 + ∂2|f(z)|2/∂y2 = 4|f'(z)|2
.

5 marks

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b

Prove that

u = x2 - y2 - 2xy - 3x + y
is harmonic function.

5 marks

Answer

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410 marks
a

Evaluate

∫01+i z2 dz
along y=x2.

5 marks

Answer

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b

Find Taylor's series expansion of

f(z) = (z+1)/(z2+2)
about the point z = i.

5 marks

Answer

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OR
5

Find the residue of

f(z) = z3/((z-1)(z-2)(z-3))
at its poles. Also evaluate
∫C f(z) dz
where C is the circle |z| = 2.5.

10 marks

Answer

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6

By integrating around a unit circle, evaluate

∫0π (dθ)/(5+4cosθ)
.

10 marks

Answer

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OR
7

Define the bilinear transformation and hence find the bilinear transformation which maps the points z = 0, -i, -1 into the points w= i, 1, 0.

10 marks

Answer

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8

Obtain the Fourier series for

f(x) = x - x2
in [-π, π] and
f(x+2π) = f(x)
. Deduce the value of
1 - 1/22 + 1/32 - 1/42 + ... = π2/12
from that Fourier series.

10 marks

Answer

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OR
9

Find Fourier Sine transform and Fourier Cosine transform of

5e-5x + 2e-2x
.

10 marks

Answer

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10

Solve the one-dimensional wave equation by the method of separation of variables and hence find all the possible solutions.

10 marks

Answer

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OR
11

An insulated rod OA of length l with insulated sides, has initial temperature

u(x,0) = f(x)
for 0 ≤ x ≤ l. Both the ends are insulated at t=0. Find the subsequent temperature distribution.

10 marks

Answer

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About this paper

This page contains the question paper of MATHEMATICS - IV from JNTU for B.Tech CSE II Year I, April/May-2023, R18.

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