11-2

9cis4pie/3

y=9sin240 degrees                       x=9cos240 degrees
y=-7.794                                     x=-4.5
z=-7.794+-4.5i

We are given 9cis4pie/3 and we have to solve it.  To solve this problem, you have to separate the cis into sin and cos.  Then you have to figure out what 4pie/3 is in degrees to make the problem easier.  To separate the cis, you have to do y=9sin240degrees and x=9cos240 degrees.  Then you just plug those two into your calculator and you get that y equals -7.794 and x equals -4.5.  Then to solve for z you get z equals -7.794+-4.5.