The function is
and
.
Find
.
Theorem 7:
\If
is a one to one differentiable function with inverse function
and
then the inverse function is
differentiable at
and
.
Find
.
Equate the function to
.
.
Substitute
in above equation.

is clearly root of the equation.
Therefore
then
.
Consider
.
Differentiate on each side with respect to
.
.
\
Power rule of derivatives :
.
From theorem 7,
.
Substitute
in above equation.

.
.