Question

Tolong dong dijelasin kenapa cos4x - 1 = -2 sin kuadrat 2x

Answer 1

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

cos4x = 1 - 2sin^2 2x

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