Question

Solve for the values in [0,2pi] to make the following true.

cos(2a) = 3 cos(a) -2

Answer 1

headdesk. :(

Answer 2

cos(a+a)=cosacos-sinasina

Answer 3

I... dont understand that equation..

Answer 4

help!

Answer 5

Read through this and see if it helps: http://oakroadsystems.com/twt/double.htm

Answer 6

You're eventually going to solve a quadratic equation for cos(a), then from there use the inverse to get a.

Answer 7

Is the interval reallly [0,2π] and not actually (0,2π] or [0,2π)? Because 0 and 2π are the same angle..

Answer 8

@silvermousme