Question

Rewrite the expression as an equivalent expression that does not contain powers of trigonometric functions greater than 1.
cos^4(x)

Answer 1

cos^4(x) = 
(cos²x)² = 
(1-sen²x)² = 
1² - 2*1*sen²x + sen^4x = 
1 - 2sen²x + sen^4x