1. The problem statement, all variables and given/known data Find the first partial derivatives ∂z/∂x and ∂z/∂y of sin(0x+5y+z)=0 at (0,0,0). 2. Relevant equations sin(0x+5y+z)=0 3. The attempt at a solution 0x+5y+z=kπ z=kπ-5y So, ∂z/∂x= 0 and ∂z/∂y= -5 What I do not understand is WHY 0x+5y+z=kπ is an acceptable equation. I found it from a solution of this online, but with no explanation. What is the significance of k and π, and why can we basically ignore the sin?