A) \[\cos 4A\]
B) \[\sin 4A\]
C) 1
D) None of these
Correct Answer: C
Solution :
\[{{\cos }^{2}}A{{(3-4{{\cos }^{2}}A)}^{2}}+{{\sin }^{2}}A{{(3-4{{\sin }^{2}}A)}^{2}}\] \[={{(3\cos A-4{{\cos }^{3}}A)}^{2}}+{{(3\sin A-4{{\sin }^{3}}A)}^{2}}\] \[={{(\cos 3A)}^{2}}+{{(\sin 3A)}^{2}}=1\]. Trick: Put\[A=\frac{\pi }{2},{{0}^{o}}\], the value of expression remains 1, therefore it is independent of A and is equal to 1.
You need to login to perform this action.
You will be redirected in
3 sec
