The number cis 75 + cis 83 + cis91 +...+ cis 147 is expressed in the form r cis(theta), where 0 <= theta < 360.

Question

Find theta in degrees.

I need help.

Answer 1

one way:

cos 75 + cos 83 + .....cos 147 = a

sin 75 + sin 83 + .... sin 147 = b

tan theta = b/a

r = sqrt (a^2+b^2)

Answer 2

I don't understand?

Answer 3

calculate a above.
calculate b above.

theta= arctan (b/a)

Answer 4

How do I calculate a and b?

Answer 5

I got 291 degrees. is that correct?

Answer 6

nvm its 111