Question

Does the inverse tangent of x^2 = 2x/(1+x^4)?

Answer 1

Depends on the surface area.

Answer 2

To get the inverse tangent, you have to find the arctan of the function.
Let f(x) = x^2 = tan y
Then, inverse tangent is given by y = arctan(x^2)
Inverse is found by solving for x.
Your answer is correct.