Use the formula for lowering powers to rewrite the expression in terms of the first power of cosine. Sin to the 4th x

Answer 1

Use the identity sin²x = (1-cos(2x))/2 with sin⁴x = (sin²x)². Make sure to keep track of your parenthesis!

Answer 2

Sin^4x = (1-Cos^2x) (1-Cos^2x) = (1+Cosx)(1-Cosx) (1+Cosx)(1-Cosx) = (1 + Cosx)^2 (1 + Cosx)^2