How do you evaluate $cos^2(pi/12)-sin^2(pi/12)$ ?

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Answer 1 · 2016-05-02T16:28:29

$cos^2(pi/12)-sin^2(pi/12)=sqrt3/2$

To evaluate $cos^2(pi/12)-sin^2(pi/12)$ , recall the identity

$cos2theta=cos^2theta-sin^2theta$

Hence, $cos^2(pi/12)-sin^2(pi/12)=cos2xx(pi/12)=cos(pi/6)=sqrt3/2$

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