Question

The number of solutions of the equation $1+{\sin }^{4}x={\cos }^{2}3x,x\in \left[-\frac{5\pi }{2},\frac{5\pi }{2}\right]$ is :

• A. 5
• B. 4
• C. 7
• D. 3

Answer 1

Answer: (A)

$1+{\sin }^{4}x={\cos }^{2}3x$
$\sin x=0\&\cos 3x=1$
$0,2\pi ,-2\pi ,-\pi ,\pi$