[m]\frac{ ∂ z}{ ∂x }=(x^2ysinx-3y)`_{x}=y\cdot ((x^2)`\cdot sinx+x^2\cdot (sinx)`)-(3y)`_{x}=y\cdot (2x\cdot sinx+x^2\cdot cosx)-0=2x\cdot y\cdot sinx+x^2\cdot y\cdot cosx [/m]
[m]\frac{ ∂ z}{ ∂y }=(x^2ysinx-3y)`_{y}=x^2\cdot sinx\cdot y`_{y}-3\cdot y`_{y}=x^2sinx - 3[/m]