AM-941

Double angle formulae

A Math · Secondary 3 · Medium · Double angle formulae

Solve the equation

\cos x=-\tfrac{1}{2}

for

0^\circ<x<360^\circ

.

$60^\circ,300^\circ$
$30^\circ,330^\circ$
$90^\circ,270^\circ$
$120^\circ,240^\circ$

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