8sin(x)cos(y) = 6
Take derivative with respect to x. Since y is a function of x, take the derivative for y as well but it is multiplied by dy/dx
chain rule
8cos(x)cos(y) - 8sin(x)sin(y)(dy/dx) = 0
solve for dy/dx
8cos(x)cos(y) = 8sin(x)sin(y)(dy/dx)
[8cos(x)cos(y)]/[8sin(x)sin(y)] = dy/dx
simplify
cot(x)cot(y) = dy/dx
