1. The problem statement, all variables and given/known data find the direction of P sub 0 in the direction of A see second post for attachment, I forgot to place it on this one. 3. The attempt at a solution I'm only worried about the part that says gy(x,y,z) = -3zexsin yz. I also don't understand the conversion of gx and gz. 1. why does cos change to sin? obviously its the derivative but why isn't the derivative being used in gx and why is it also used in gz 2. if they're taking the derivative then it doesn't look like the product rule is being used. why not? 3. I would think they would be using u substitution with the x in ex but I'm better at using u substitution with integrals than with derivatives. I'm pretty sure this is the explanation for why there is a -3z and a -3y in gy and gz. I understand where the negative sign comes from, it's because the derivative of cos in -sin. But I don't understand where the z and y comes from.