Simplify the expression.
-$2 \cos ^ { 2 } 4 x - 1$
A) $2 \sin 4 x$
B) $\cos 8 x$
C) $\frac { 1 } { 2 } \sin 16 x$
D) $\cos 4 x$

Name: Simplify the expression. -$2 \cos ^ { 2 } 4 x - 1$ A) $2 \sin 4 x$ B) $\cos 8 x$ C) $\frac { 1 } { 2 } \sin 16 x$ D) $\cos 4 x$
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Question

Quizplus · Accepted Answer

This expression can be simplified using the double angle formula for cosine, which states that $\cos(2\theta) = 2\cos^2(\theta) - 1$. By substituting $4x$ for $\theta$, we get $\cos(8x)$, which matches choice B.

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Simplify the Expression $2 \cos ^ { 2 } 4 x - 1$