calculus help

[jesslynz]

someone please help me with this problem
the volume of a cone is 18pi cubic metres. find the minimun length of the slant edge.

 

[MarkFL]

What is the length of the slant edge in terms of the radius and height of the cone?

 

[DrPhil]

someone please help me with this problem
the volume of a cone is 18pi cubic metres. find the minimun length of the slant edge.

It is impossible to see where you are stuck if you show no work.

Write the formula for the volume of the cone, in terms of r and h.
Write the formula for the slant length of the cone, in terms of r and h.

What methods do you know to find the derivative of slant length?