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Code :9ABS302 II B.Tech I semester (R09) Regular Examinations, November 2010 MATHEMATICS-III

(Electrical & Electronics Engineering, Electronics & Instrumentation Engineering, Electronics & Control Engineering, Electronics & Communication Engineering, Electronics & Computer Engineering)

Time: 3 hours

Max Marks: 70 Answer any FIVE questions All questions carry equal marks ?????

1. (a) Show that

R1

√ √ (p) (q) (1 + x)p−1 (1 + x)q−1 dx = 2p+q−1 √ . (p+q)

−1

(b) Show that nx Jn (x) + Jn1 (x) = Jn−1 (x) 2. (a) State the necessary condition for f(z) to be analytic in cartesion co-ordinates. 3

3

(1−i) f (z) = x (1+i)−y , (z 6= 0) 2 +y 2 x (b) Prove that the function f(z) defined by is continuous and = 0 , (z = 0) the Cauchy-Riemann equations are satisfied at the origin, yetf 1 (0) does not exist.

3. (a) Find the real part of the principle value ilog(1+i) . (b) Find real and imaginary parts of i. cos z ii. tan z 4. (a) Verify Cauchy’s theorem for the function f (z) = 3z 2 + iz − 4 if C is the square with vertices at 1 ± i and − 1 ± i . R z−3 (b) Evaluate z2 +2z+5 dz where C is the circle c

i. |z| = 1 ii. |z + 1 − i| = 2 5. (a) Find Taylor’s expansion of f (2) =

2z 3 +1 z 2 +z

about the point

i. z=i ii. z=1. (b) Obtain all the Laurent series of the function

7z−2 (z+1)z(z−2)

about z0 = −1

6. (a) State and prove Cauchy’s Residue theorem. R2π (b) Show that a+bdθcos θ = √a2π 2 −b2 (a > |b| > 0) 0

7. Show that all the roots of z 5 + 3z 2 = 1 lie inside the circle |z| < lie inside the circle |z| < 3/4 8. (a) Show that the relation w = in the w-plane.

5−4z 4z−2

√ 3 4.and that two of its roots

transform the circle|z| = 1 into a circle of radius unity

(b) Find the bilinear transformation which maps the points (2, i, −2) into the points (1, i, −1). ?????

2 II B.Tech I semester (R09) Regular Examinations, November 2010 MATHEMATICS-III (Electrical & Electronics Engineering, Electronics & Instrumentation Engineering, Electronics & Control Engineering, Electronics & Communication Engineering, Electronics & Computer Engineering)

Time: 3 hours

Max Marks: 70 Answer any FIVE questions All questions carry equal marks ?????

1. (a) Prove that

R1 0

2

√x dx 1−x4

×

R1 0

√ dx 1+x4

=

π √ 4 2

(b) Prove that J−n (x) = (−1)n Jn (x) , where n is a positive integer. 2. (a) If ´ harmonic functions in a region R, prove that the function ³ U(x,y)´ and ³V(x,y) are ∂v ∂u ∂v ∂u − ∂x + i ∂x + ∂y is an analytic function. ∂y (b) Determine the analytic function whose real part is i. ex cos y ii. e2x (x cos 2y − y sin 2y) 3. (a) If Sin (θ + iα) = cosα + i sin α, then prove that Cos4 θ = sin2 α . ¡ ¢ 2 (b) If cosec π4 + iα = u + iv, prove that (u2 + v 2 ) = 2 (u2 − v 2 ) . 4. (a) Evaluate

1+i R

(x2 − iy)dz along the paths

0

i. y = x ii. y = x2 (b) Using Cauchy’s integral formula, evaluate

R c

36. 5. (a) Show that when |z + 1| < 1, z −2 = 1 +

∞ P

z4 dz (z+1)(−i)

where C is the ellipse 9x2 + 4y 2 =

(n + 1) (z + 1)n

n=1

(b) Find the Laurent series expansion of the function f (z) =

z 2 −6z−1 (z−1)(z−3)(z+2)

6. (a) Find the poles of f (z) and the residues of the poles which lie on imaginary axis if z 2 +2z f (z) = (z−1) . 2 2 (z +4) R 2 dz where c is the circle |z| = 1 using Residue theorem. (b) Evaluate (2z+1) 4z 3 +z c

7. (a) Show that one root of the equation z 4 + z + 1 = 0 lies in the first quadrant. (b) Apply Rouche’s theorem to determine the number of roots of f (z) = z 4 − 5z + 1 within annulus region 1 < |z| < 2 . 8. (a) Find the image of the rectangle R : −π < x < π, 21 < y < 1 under the transformation W=sinz. (b) Determine the bilinear transformation that maps the points 1-2i, 2+i, 2+3i respectively 2+2i, 1+3i, 4. ?????

3 II B.Tech I semester (R09) Regular Examinations, November 2010 MATHEMATICS-III (Electrical & Electronics Engineering, Electronics & Instrumentation Engineering, Electronics & Control Engineering, Electronics & Communication Engineering, Electronics & Computer Engineering)

Time: 3 hours

Max Marks: 70 Answer any FIVE questions All questions carry equal marks ?????

q¡ ¢p p q¡ ¢ 1 1 2n−1 = 2 1. (a) Show that . (2n) (n) n + 2 2 (b) Prove that J0 (x) = 1 −

x2 22

+

x4 22 .42

−

x6 22 .42 .62

+−−−−−

2. (a) Prove that Zn (n is a positive integer) is analytic and hence find its derivative. (b) Show that the function u = e−2xy sin (x2 − y 2 ) is harmonic, find the conjugate function ’v’ and express u + iv as an analytic function of z. 3. (a) Separate the real and imaginary parts of i. cosec z ii. cot z

√ ¢¡ √ ¢ ¡ (b) Find all principal values of 1 + i 3 1 + i 3 4. (a) Evaluate

3+i R

z 2 dz, along

0

i. The line y = x3 ii. Parabola x = 3y 2 R z2 −2z−2 (b) Evaluate (z 2 +1)2 Z dz where C is |Z − i| = c

5. (a) Find the Laurent series of

7z−2 (z+1)z(z−2)

1 2

using cauchy’s integral formula.

in the annulus 1 < |Z + 1| < 3 .

(b) Expand f (z) = e1+z in powers of (Z - 1). H zdz 1 6. (a) Evaluate c (z−1)(z−2) 2 where C : |z − 2| = 2 . (b) Evaluate

R2π 0

dθ (5−3 sin θ)2

using residue theorem.

7. (a) Determine the number of roots of the equation 2z 5 − 6z 2 + z + 1 = 0 in the region 1 ≤ |z| < 2. (b) Use Rouche’s theorem to show that the equation z 2 + 15z + 1 = 0 has one root in the disk |z| > 23 and four roots in the ammulus 23 < |z| < 2 . 8. (a) Find the image of the infinite strip bounded by x = 0 and x = w = cos z.

π 4

under the transformation

(b) Find the bilinear transformation which maps vertices (1 + i, −i, 2 − i) of the triangle T of the Z- plane into the points (0,1,i) to the w-plane. ?????

4 II B.Tech I semester (R09) Regular Examinations, November 2010 MATHEMATICS-III (Electrical & Electronics Engineering, Electronics & Instrumentation Engineering, Electronics & Control Engineering, Electronics & Communication Engineering, Electronics & Computer Engineering)

Time: 3 hours

Max Marks: 70 Answer any FIVE questions All questions carry equal marks ?????

1. (a) Evaluate 4

R∞ 0

x2 dx 1+x4

using β − Γ functions. n

n

d 2 (b) Prove that Pn (x) = 2x1n! dx n (x − 1) . ³ 2 ´ ∂ ∂2 2. (a) Show that ∂x2 + ∂y2 log |f 1 (z)| = 0 where f(z) is an analytic function.

(b) Prove that u = e−x [(x2 − y 2 ) cos y + 2xy sin y] is harmonic and find the analytic function whose real part is u. 3. (a) Find all the roots of sinz=2. (b) If tan(x+iy)=A+iB, show that i. A2 + B 2 + 2A cot 2x = 1 ii. A2 + B 2 − 2B coth 2y + 1 = 0 R 4. (a) Show that (z + 1)dz = 0 where c is the boundary of the square whose vertices at the c

points z = 0, z = 1, z = 1 + i, z = i. R e2z (b) Evaluate (z−1)(z−2) dz, where C is the circle |z| = 3. c

5. (a) Expand f (z) =

z 2 −4 z 2 +5z+4

valid for |z| < 1 .

(b) obtain the Laurent’s series which represents the function

1 (1+z 2 )(z+2)

when

i. |z| < 1 ii. 1 < |z| < 2 R z−2 dz where c is |z| = 2 using Residue theorem. 6. (a) Evaluate z(z−1) c

(b) Evaluate

R2π 0

sin 3θ dθ 5−3 cos θ

using Residue theorem.

7. (a) Show that the equation z 4 + 4 (1 + i) z + 1 = 0 has one root in each quadrant. (b) State and prove fundamental theorem of algebra. 8. (a) Find the image of the line x = 4 in z-plane under the transformation w = z 2 . (b) Find the bilinear transformation that maps the points 1, i, -1 into the points 2, i, -2. ?????