Question

The value of $\sin {12}^{\circ }\cos {78}^{\circ }+\cos {12}^{\circ }\sin {78}^{\circ }$ is ..........

• A. 0
• B. 1
• C. -1
• D. None of these

Answer 1

Answer: (B)

1

$\sin 12°\cos 78°+\cos 12°\sin 78°$

$=\sin 12°\cos (90°-12°)+\cos 12°\sin (90°-12°)$

$=\sin 12°\sin 12°+\cos 12°\cos 12°$

$={\sin }^{2}12°+{\sin }^{2}12°$

$=1$

Hence, the answer is $1.$