revising for an exam and have the question let I=∫lim ∞ to 0 e-x2 dx. since x is a dummy variable here, replace it with y to get a second expansion for I. Multiply these two together to get a double integral for I2. Transform into polar co-ordinates noting that dxdy corresponds to r dr d♂. Carry out the integrations and deduce I. Right so i got the new equation and multiplied together to get r2cos2♂+r2sin2♂ giving me a lovely 1*r2 and giving e-r2 after which i get stuck because i dont understand the limits on the first integral♂ change from inf-0 to pi/2-0 answers on a postcard please!