- #1

Cod

- 325

- 4

Just to refresh your minds, the double-angle formulas:

sin2x = 2(sinx)(cosx)

cos2x = cos^2x - sin^2x = 1 - 2sin^2x = 2cos^2x-1

tan2x = 2tanx/1-tan^2x

The book example:

If cosx = -2/3 and x is in quadrant II; find sin2x and cos2x.

If someone could explain the processes when using these formulas to solve problems, I'd greatly appreciate it. The book just isn't helping me any.