Q. If $\sin{x + \sin{y = a}}$ and $\cos{x + \cos{y = b}}$, then $\tan\left( \frac{a + y}{2} \right)$ is equal to

A) $\frac{ab}{a + b}$
B) $\frac{a}{b}$
C) $\frac{b}{a}$
D) None of these
Explanation

(b)
$\frac{\sin{x + \sin y}}{\cos{x + \cos y}} = \frac{a}{b}$
$\Rightarrow \ \ \ \frac{2\sin{\left( \frac{x + y}{2} \right)\cos\left( \frac{x - y}{2} \right)}}{2\cos{\left( \frac{x + y}{2} \right)\cos\left( \frac{x - y}{2} \right)}} = \frac{a}{b}$
$\Rightarrow \ \tan\left( \frac{x + y}{2} \right) = \frac{a}{b}$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.