# What is the derivative of e^cosx+e^siny=1/4?

What to you mean exactly? You can calculate the derivative of a function in the form $y = f \left(x\right)$ (or, in your case, $z = f \left(x , y\right)$, but what do you mean with the derivative of something like $f \left(x , y\right) = c$? You only want to know which the derivative of ${e}^{\setminus \cos \left(x\right)} + {e}^{\setminus \sin \left(x\right)}$ is? Please explain better and I'll be glad to help