1. In polar form, z = 1 + 3i =

   (a) 2 cis /₃   ; (b) 2 cis (- 2/₃)   ; (c) 2 cis 2/₃   .

2. If z = 2 cis 5/₄, then z =

   (a) 1 + i   ; (b) -1 - i    ; (c)  -1 + i    .

3. A square root of -i is

   (a) 1   ; (b) cis 3/₈   ; (c) cis 3/₄   .

4. Geometrically, the powers of cis /₅ generate all the vertices of a regular pentagon.

   (a) True   ; (b) False   .

Notes