Actually, I didn't find the derivative of the first term of the first term.
Sin (2xy) I simply put as Cos (2xy). Why are you taking the derivative of the inside function ?
Chain rule, just as e^i*pi said. Always remember to use the chain rule whenever you see a function in the parenthesis. If it isn't just , then you have to apply the chain rule. In this case, you have to apply a combination of the chain rule and implicit differentiation. So try to find the derivative