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JNTU B.Tech II MATHEMATICS-IV Previous Question Paper (March - 2022 - R16)

B.Tech | II | I | R16 | March - 2022

Answer PaperPaper Code: 133BDMaximum Marks: 75Time: 3 Hours

Answer any five questions. All questions carry equal marks.

Main

115 marks
a

Find the analytic function whose real part is e-x(x sin y - y cos y)

8 marks

Answer

Given the real part u(x, y) = e-x(x sin y - y cos y). We use the Milne-Thomson method to find the analytic function f(z) = u + iv. First, compute the partial derivatives:

ux = -e-x(x sin y - y cos y) + e-x(sin y) = e-x((1-x)sin y + y cos y)
uy = e-x(x cos y - (cos y - y sin y)) = e-x((x+y)cos y - cos y) = e-x((x+y-1)cos y)

The derivative of the analytic function is f'(z) = ux(z, 0) - i uy(z, 0). Substituting y = 0:

ux(z, 0) = e-z((1-z)sin 0 + 0 cos 0) = 0
uy(z, 0) = e-z((z+0-1)cos 0) = e-z(z-1)

Thus, f'(z) = 0 - i(e-z(z-1)) = i(z-1)e-z. Integrating with respect to z:

f(z) = i ∫ (z-1)e-z dz = i [ (z-1)(-e-z) - (1)(e-z) ] + C = i(z e-z - e-z + e-z) + C = i z e-z + C
b

Find the value of ‘a’ if cos(ax)sinh(y) is harmonic.

7 marks

Answer

A function φ(x, y) is harmonic if it satisfies Laplace's equation: φxx + φyy = 0. Given φ = cos(ax)sinh(y):

φx = -a sin(ax)sinh(y)
φxx = -a2 cos(ax)sinh(y)
φy = cos(ax)cosh(y)
φyy = cos(ax)sinh(y)

Substituting into Laplace's equation:

-a2 cos(ax)sinh(y) + cos(ax)sinh(y) = 0
cos(ax)sinh(y) (1 - a2) = 0

For this to hold for all x and y, we must have 1 - a2 = 0, which implies a2 = 1, so a = ±1.

215 marks
a

Evaluate the integral of 1/(e^z - 1) over the contour |z|=2.

7 marks

Answer

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b

Find the poles and the residues at each pole of (z^2+1)/(z^2-2z).

8 marks

Answer

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3

Evaluate using the Residue theorem the integral of (z^2-2z)/(z^2+10z+9) over the circle |z|=2.

15 marks

Answer

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4

Expand 1/((z-1)(z-2)) about:

15 marks
a

|z| < 1

5 marks

Answer

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b

1 < |z| < 2

5 marks

Answer

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c

|z| > 2

5 marks

Answer

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515 marks
a

Find the image of 1 < x < 2 under the transformation w = ez.

7 marks

Answer

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b

Find the bilinear mapping which maps the points z = 1, i, -1 into infinity, -i, 0.

8 marks

Answer

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615 marks
a

Obtain the Fourier series for the function f(x) = 0 in (-pi, 0) and x in (0, pi).

7 marks

Answer

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b

Find the Fourier transform of f(x) = 1-|x| for |x|<1 and 0 for |x|>1, and hence evaluate the integral of sin^2(s)/s^2 from 0 to infinity.

8 marks

Answer

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715 marks
a

Obtain a cosine series for the function f(x) = x for 0 < x < pi/2 and f(x) = pi-x for pi/2 < x < pi.

7 marks

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b

Find the Fourier sine transform of e-|x| and hence evaluate the integral of sin(mx)/(1+x^2) from 0 to infinity.

8 marks

Answer

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8

Solve the boundary value problem utt = a2uxx, 0 < x < l, t > 0 with u(0,t)=0, u(l,t)=0, u(x,0)=0, and ut(x,0) = sin(3*pi*x/l).

15 marks

Answer

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