Q. The function $f(x) = \frac{1 - \sin{x + \cos x}}{1 + \sin{x + \cos x}}$ is not defined at$x = \pi$. The value of $f(\pi)$, so that $f(x)$ is continuous at $x = \pi$, is

A) -1/2
B) ½
C) -1
D) 1
Explanation

(c)
$\lim_{x \rightarrow \pi}\ \frac{(1 + \cos{x) - \sin x}}{(1 + \cos{x) + \sin x}}\$
$= \lim_{x \rightarrow \pi}\frac{2\cos^{2}{x/2 - 2(\sin{x/2)\ cos\ x/2}}}{2\cos^{2}{x/2 + 2(\sin{x/2)\ cos\ x/2}}}$
$= \lim_{x \rightarrow \pi}\tan{\left( \frac{\pi}{4} - \frac{\pi}{2} \right) = - 1}$
Since, $f(x)$ is continuous at $x = \pi$
$\therefore\ \ f(\pi) = \lim_{x \rightarrow \pi}\ f(x) = - 1$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

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