Question
Evaluate $: \sin^2 40^\circ - \cos^2 50^\circ$
✓
Answer
$\sin^2 40^\circ - \cos^2 50^\circ$
$= \sin^2(90^\circ - 50^\circ) - \cos^2 50^\circ$
$= \cos^250^\circ - \cos^250^\circ$
$= 0$
$= \sin^2(90^\circ - 50^\circ) - \cos^2 50^\circ$
$= \cos^250^\circ - \cos^250^\circ$
$= 0$
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