Solve $$\int_0^1\int_0^u(tan^2x+y)^{1\over2}dxdy$$ where $0<u<{\pi\over2}$
My attempt was to use Fubini's thm, but when I solved this $$\int_0^{\pi\over2}\int_0^1(tan^2x+y)^{1\over2}dydx$$ I got a few undefined terms. I assume my limits of integeration is wrong, but i cannot understand why.