Question

Rewrite 8 cos^2 x as an equivalent expression that does not contain powers of trigonometry functions greater than 1.

Answer 1

You can use a power-reducing formula for this:

http://en.wikipedia.org/wiki/List_of_trigonometric_identities#Power-reduction_formula

Answer 2

See if you can use this to help you:

cos^2(x)=(1+cos(2x))/2