1. The problem statement, all variables and given/known data Well iv been looking around for a similar problem and found the use of the following equation. what I would like to know is if the following equation is actually correct? I believe it may be a extension of the Fubini's theorem but cant find a reference or derivation on the net. any help would be great thanks I=∫0∞ e-x2 Show I=sqrt(pi/4) by first evaluating I^2 2. Relevant equations [∫f(x) dx]^2 = ∫∫f(x)f(y) dxdy ? link- https://www.physicsforums.com/showthread.php?t=243670 3. The attempt at a solution I2=∫∫e-2x2dxdy?