Question 28

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waecmaths question: 

If $\cos {{(x+25)}^{o}}=\sin {{45}^{o}}$, find the value of x

Option A: 

20

Option B: 

30

Option C: 

45

Option D: 

60

waecmaths solution: 

$\begin{align}  & \cos (x+{{25}^{\circ }})=\sin {{45}^{\circ }} \\ & \cos (x+{{25}^{\circ }})=\sin [90-(x+{{25}^{\circ }})]=sin{{45}^{\circ }} \\ & \sin ({{65}^{\circ }}-x)=sin{{45}^{\circ }} \\ & {{65}^{\circ }}-x={{45}^{\circ }} \\ & x={{20}^{\circ }} \\\end{align}$

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