Question

Question #4e1e9

Answer 1

This identity is incorrect. The correct version is given below.

Explanation:

In order to prove this identity, we need to use the double angle formula:

`cos2A=cos^2A-sin^2A=2cos^2A-1`
`=1-2sin^2A`

`cos4x=1-2sin^2 2x`

`cos2x = 1-2sin^2 x`

`cos4x+cos2x =1-2sin^2 2x + 1-2sin^2 x`
`=2-2sin^2 2x - 2sin^2 x` ΟΕΔ