21. If z1 = 24 + 7i and |z2| = 6, then the least value of |z1 + z2| is:
A. 31
B. 19
C. −19
D. −13
22. |az+b|/|bz+a| =1, for |z| =?
A. 1
B. 0
C. 2
D. −1
23. Locus of the points satisfying Re(iz) = 3 is:
A. a line parallel to x-axis
B. a line parallel to y-axis
C. a circle
D. a parabola
24. For all integers n, we have:
A. (cos θ + isin θ)^n = cos nθ + isin nθ
B. (cos θ + isin θ)^n = cos nθ − isin nθ
C. (cos θ − isin θ)^n = cos nθ + isin nθ
D. (cos θ + isin θ)^−n = cos nθ + isin nθ
25. The value of ( √3−i/√3+i )^6 is:
A. 0
B. 1/2
C. 1 ✓
D. −1
26. For any integers n, we have (sin x + i cos x)^n =
A. sin n( π/2 − x) + i cos n( π/2 − x)
B. cos n( π/2 − x) + isin n( π/2 − x)
C. sin n( π/2 + x) + i cos n( π/2 + x)
D. sin n( π/2 + x) + i cos n( π/2 + x)
27. If x = cos θ + isin θ, then the value of 1/x =
A. cos θ + isin θ
B. sin θ + i cos θ
C. cos θ − isin θ
D. sin θ − i cos θ
28. If x = cos θ + isin θ, then the value of 1/x^n=
A. cos nθ + isin nθ
B. sin nθ + i cos nθ
C. cos nθ − isin nθ
D. sin nθ − i cos nθ
29. If x = cos θ + isin θ, then the value of x^n + 1/x^n=
A. 2isin nθ
B. 2i cos nθ
C. 2 cos nθ
D. 2 sin nθ