Suppose
f is a real valued function which is a composite of three functions u, v and w; i e ,
f = (w o u) o v If t = v (x) and s = u (t), then
( o )
df
d w u
dt
dw ds
dt
dx
dt
dx
ds
dt
dx
=
⋅
=
⋅
⋅
provided all the derivatives in the statement exist