JEE PYQ: Limits Question 10
Question 10 - 2020 (02 Sep Shift 2)
$\lim_{x \to 0} \left(\tan\left(\frac{\pi}{4} + x\right)\right)^{1/x}$ is equal to:
(1) $e$
(2) $2$
(3) $1$
(4) $e^2$
Show Answer
Answer: (4)
Solution
$\lim_{x\to 0} e^{\frac{1}{x}\ln\tan(\frac{\pi}{4}+x)} = e^{\lim_{x\to 0}\frac{1}{x}\ln\frac{1+\tan x}{1-\tan x}}$. Using expansion: $= e^{\lim_{x\to 0}\frac{\tan x}{x} \cdot \frac{2}{1-\tan x}} = e^2$.