Question

Evaluate the function f(x) = sec(x - pi/2) for x = 0.

Answer 1

$\sec\left(0-\dfrac{\pi}{2}\right)=\sec\left(-\dfrac{\pi}{2}\right)=\dfrac{1}{\cos \left(-\dfrac{\pi}{2}\right)}=\dfrac{1}{0}$

So, the function $f(x)$ for $x=0$ is undefined.