Power Reduction Formulas/Cosine to 4th

Theorem

 * $\cos^4 x = \dfrac {3 + 4 \cos 2 x + \cos 4 x} 8$

where $\cos$ denotes cosine.

Also defined as
This result can often be seen as:
 * $\cos^4 x = \dfrac 3 8 + \dfrac {\cos 2 x} 2 + \dfrac {\cos 4 x} 8$