- #1

- 257

- 2

But is this a valid mathematical procedure? $$\int_a^b \frac{dx}{1-x^2}=i \int_{-ia}^{-ib} \frac{du}{1+u^2}$$

Do those limits even make sense? They don't make sense in terms of area under a curve. But the integral over real numbers is inverse tangent, and if you just plug in the imaginary number into inverse tangent, you get the right answer?