The radius of the sphere is
.
The radius of the cone is
.
Height of the cone is
.
Center of the Sphere is
.
Draw a digram using the above information.
\
From the diagram.
\


Apply pythagorean theorem to right angle triangle
.

Volume of the cone : 
Substitute
in the above equation.

Differentiate with respect to
.

Equate
to zero.

Substitute 
.

Substitute
and
in
.

Volume of the cone is
.
Volume of the cone is
.