A) \[x\cos \theta -y\sin \theta =a\cos \ 2\theta \]
B) \[x\cos \theta +y\sin \theta =a\cos \ 2\theta \]
C) \[x\sin \theta +y\cos \theta =a\cos \ 2\theta \]
D) None of these
Correct Answer: A
Solution :
\[x\cos \theta -y\sin \theta =a\text{ }({{\cos }^{4}}\theta -{{\sin }^{4}}\theta )=a\cos 2\theta \].You need to login to perform this action.
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