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Doctors Medicines MCQs Q&A

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As $sintheta=-12/13$ i.e. negative and $costheta$ is positive, $theta$ lies in $Q4$ i.e. $(3pi)/2< theta < 2pi$

$costheta=sqrt(1-(-12/13)^2)-sqrt(1-144/169)=sqrt(25/169)=5/13$

Hence, $sin2theta=2sinthetacostheta=2xx(-12/13)xx5/13=-120/169$

and $cos2theta=cos^theta-sin^2theta=25/169-144/169=-119/169$

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