how do you find the exact value of cos 120 without using a calculator ?
exact value watch
- Thread Starter
- 18-01-2010 19:39
- 18-01-2010 19:47
Cos(60+60) then expand or just use double angle rule which would be 1-2sin^2(60)
- 18-01-2010 19:48
use the identity for cos2x with x=60, you should know/be able to work out cos60 and sin60