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$\begingroup$ How do you simplify $\cos^4(x)$ using the power reducing formula?
$\endgroup$ 1 Answer
$\begingroup$ You probably mean using $\cos^2x=(1+\cos2x)/2$, so
$$
\cos^4x=\frac{1}{4}(1+2\cos2x+\cos^22x)
$$
Now apply the same to $\cos^22x$.
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