# The Average Radius

**Calculus**Level 5

A point \(P\) moves on an ellipse whose foci are \(S\) and \(S'\). Find the mean radius of the incircle of the triangle \(\Delta PSS'\) averaged over one complete revolution of point \(P\) on the ellipse.

**Note:** The lengths of the semi-major and semi-minor axes of the ellipse are 5 and 4, respectively.