waecmaths question:
If tan y = 0.404, where y is acute, find cos 2y
Option A:
0.035
Option B:
0.719
Option C:
0.808
Option D:
0.927
waecmaths solution:
$\begin{align} & y={{\tan }^{-1}}(0.404)=21.9987 \\ & \cos 2y=\cos 2(21.9987)=cos43.9974\simeq 0.719 \\\end{align}$
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