Question

If $\sin 2A=\cos A$ then the value of A is

• A. ${30}^{\circ }$
• B. ${45}^{\circ }$
• C. ${60}^{\circ }$
• D. ${75}^{\circ }$

Answer 1

Answer: (A)

${30}^{\circ }$

We know that $\sin 2A=2\sin A\cos A$
Then from $\sin 2A=\cos A$, we get
$2\sin A=1$
$\sin A=1/2$
So, $A={30}^o$..........(Since $\sin {30}^o=1/2$)