AM-2499

Double angle formulae

A Math · Secondary 4 · Hard · Double angle formulae

Solve

\sin 2x + 2\cos^2 x = 0

for

0 \le x \le 2\pi

.

$x=\tfrac{\pi}{2},\tfrac{3\pi}{2},\tfrac{3\pi}{4},\tfrac{7\pi}{4}$
$x=\tfrac{\pi}{2},\tfrac{3\pi}{2}$ only
$x=\tfrac{\pi}{4},\tfrac{5\pi}{4},\tfrac{3\pi}{2}$
$x=\tfrac{\pi}{4},\tfrac{3\pi}{4},\tfrac{5\pi}{4},\tfrac{7\pi}{4}$

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