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Question #e5caf

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May 1, 2017

$cos (\frac{2 π}{5})$ $cos((2pi)/5)$

Explanation:

$Reminder sin θ = cos (\frac{π}{2} - θ)$ $color(orange)"Reminder " sintheta=cos(pi/2-theta)$

$\Rightarrow sin (\frac{π}{10}) = cos (\frac{π}{2} - \frac{π}{10}) = cos (\frac{2 π}{5})$ $rArrsin(pi/10)=cos(pi/2-pi/10)=cos((2pi)/5)$

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