Hi y'all. Carlo T here with a little mathematical puzzler. Here's the big ol' question, are you folks ready? let phi:(0, infty)x(0, 2*pi)x(-pi/2, pi/2)->R^3 be defined by phi(r,alpha,beta)=(r*cos(alpha)*cos(beta), r*sin(alpha)*cos(beta), r*sin(beta)). Calculate the pullback phi*(xdy) I've calculated phi*(dx), phi*(dy) and phi*(dz) but am not sure where to go from here. For example, is there a way of rewriting phi*(xdy) using one of the pullback properties? Get your noggins round that one brothers. Peace out, from the C to the T to the remBath!!!