How do you verify $costhetacos(-theta)-sinthetasin(-theta)=1$ ?

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Answer 1 · 2016-11-17T21:09:11

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$cos theta cos(-theta)-sin theta sin(-theta)=1$

Use the odd and even property. That is, $cos (-theta)=cos theta$ and $sin(-theta)=-sin theta$

Left Hand : $=cos theta cos(-theta)-sin theta sin(-theta)$

$=cos theta cos(theta)+sin theta sin(theta)$

$=cos^2 theta+sin^2 theta$

$=1$

$:.=$ Right Side

How do you verify costhetacos(-theta)-sinthetasin(-theta)=1costhetacos(-theta)-sinthetasin(-theta)=1?