Question

What is the equation of the tangent line of `f(x) =tan^2x*sec2x-e^xcosx` at `x=pi/4`?

Answer 1

We have

`y = tan^2(x)sec(2x) - e^(x)cos(x)`

However at `pi/4`, `sec(2x)` is not defined, so the function as whole is not defined and therefore there is no tangent line at that point.