Question

What is the equation of the line normal to `f(x)=xtanx` at `x=pi/2`?

Answer 1

There is no such thing.

Explanation:

`pi/2` is not in the domain of `tanx`, so it is not in the domain of `f`.

There is no point on the graph with `x=pi/2`, so there is no line normal to the graph at `x=pi/2`.