Originally Posted by
Shyam 3. equation of curve, $\displaystyle y = 3 \tan x$
slope of tangent, $\displaystyle \frac{dy}{dx}=3 \sec^2 x$
$\displaystyle \left[\frac{dy}{dx}\right]_{(x=\frac{\pi}{4})}=3 \sec^2 \left(\frac{\pi}{4} \right)$
$\displaystyle slope=\left[{\frac{dy}{dx}}\right]_{(x=\frac{\pi}{4})}= 6$
equation of tangent at $\displaystyle \left( \frac{\pi}{4}, 3 \right)$ is
$\displaystyle x-\frac{\pi}{4}=6(y-3)$
$\displaystyle x-6y+18-\frac{\pi}{4}=0$
$\displaystyle x-6y+\frac{72-\pi}{4}=0$