An isosceles triangle is circumscribed about a circle of radius $\displaystyle R$. Express the perimeter of the triangle as a function of its altitude, and show that the perimeter is a minimum when this altitude is $\displaystyle 3R$.

This should not be that hard, but I cannot for the life of me figure out the equation in terms of the altitude and radius ONLY. I have too many variables. Thanks for you help.