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SAT® Subject Test in Math 1 & 2

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Moderate

Double Angle of Secant

SATSTM-5EXYAW

If $2a=\sec(2x)\cos(2x)$, then $a=$?

A

$\text{sec x cos x}$

B

$4$

C

$0.5$

D

$1$

E

$\cos(4x)$