Question

http://screensnapr.com/v/EB3Gyd.png
One of my last questions for the day (about two left)

Answer 1

Cos20 = Cos^2(10)-Sin^2(10)
Sin20 = 2Sin(10)Cos(10)

Answer 2

use those double angle formulas, do the algebra, and u're good to go (i think).

Answer 3

Double angle formulas? What? Haha, I think you're going a little too into it :0

Answer 4

well, or u can use wolframalpha.com

Answer 5

How exactly would i type this one into there?

Answer 6

hold on..

Answer 7

GOT THE ANSWER

Answer 8

10sqrt(3)+10i

Answer 9

http://www.wolframalpha.com/input/?i=20*%28Cos%2820%29%2Bi*Sin%2820%29%29*%28Cos%2810%29%2Bi*Sin%2810%29%29
yea it's C