Home work: 05 Mohammad Hassan Murad, MNS, BRACU
MAT 215, Spring’15 Mathematics III
Problems based on Taylor, Laurent’s series and residue1
1. Expand each of the following functions in a Taylor series about the indicated points
(a) e−z at z = 0
π
(b) cos z at z =
2
(c) z 3 − z 2 + 4z − 2 at z = 2
(d) zez at z = −1.
z
2. Expand f (z) = in a Laurent series valid for
(z − 1)(2 − z)
(a) |z| < 1
(b) 1 < |z| < 2
(c) |z| > 2
(d) |z − 1| > 1
(e) 0 < |z − 2| < 1.
z2
I
3. Evaluate 2
dz using the residue at the poles, where C is the unit circle |z| = 1.
2z + 5z + 2
C
z2 + 4
I
4. Evaluate dz using the residue at the poles around the circle |z| = 3.
z3 + 2z 2 + 2z
C
z2 − z + 2
I
1
5. Evaluate dz using the residue at the poles around the circle |z| = 4.
2πi z4 + 10z 2 + 9
C
zeiπz
I
6. Evaluate dz using the residue at the poles where C is the upper half of the circle |z| = 2.
(z 2 + 2z + 5)(z 2 + 1)2
C
1 Follow the class lectures