Question 26

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waecmaths question: 

If $\sin 3y=\cos 2y$ and ${{0}^{\circ }}\le y\le {{90}^{\circ }}$, find the value of y

Option A: 

18o

Option B: 

36o

Option C: 

54o

Option D: 

90o

waecmaths solution: 

$\begin{align}  & sin\theta =cos(90-\theta ) \\ & \sin 3y=\cos (90-3y)=\cos 2y \\ & \cos (90-3y)=\cos 2y \\ & 90-3y=2y \\ & 5y=90 \\ & y={{18}^{\circ }} \end{align}$

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