Question

evaluate the derivative of the function at the point (1,1)
f(x)=tanxcotx

Answer 1

0

Answer 2

tan=sin/cos
cot=cos/sin
so tanxcotx=1
and derivative of constant is zero every where

Answer 3

f is not defined at \[x=k\frac{\pi}{2}\text{ where }k\in\mathbb{Z}\]

so the derivative does not exist for those values.