Find the partial derivatives of the following functions:
a. f(x,y,z)=xy
b. f(x,y,z)=z
c. f(x,y)=sin (xsin (y))
d. f(x,y,z)= sin (x sin (y sin(z)))
e. f(x,y,z)=xy2
f. f(x,y,z)=xy=z
g. f(x,y,z)=(x +y)2
h. f(x,y)= sin(xy)
i. f(x,y)= (sin (xy)) cos(3)