1. The problem statement, all variables and given/known data I am to use a substitution of variables u = x, v = x + 2y to evaluate the surface integral int(0,1/2)int(0,1-y) exp(x/(x+y))dxdy where int(a,b) means integral sign with lower limit a and upper limit b. 2. Relevant equations 3. The attempt at a solution I used the substitution and calculated the Jacobian to be 1/2. However, in the new variables, the integral is now int(0,1/2)int(0,1+u-v)exp(u/v)dudv Both variables appearing in one of the integrals doesn't seem right to me - what has gone wrong with the calculation?