Diagonaliseation a square matrix of any order.

Let A be a square matrix of order n. Then (A - kI)X = 0, where k is called eigen value and I is called Identity matrix of order n, X is called eigen vector, is called characterstic equation. The equation A - kI = 0 gives n values of k and for each value of k, n column vectors. P be the square matrix of order n formed by the n column vectors.

The diagonal matrix of A = (inverse of P)AP.

Liquid Level of Horizontal Tank

Hello,
I want to calculate the liquid level of a horizontal cylindrical tank. Consider the equation :

V=L{(Pi)R^2-R^2ArcCos[(R-h)/R]+(R-h)Sqrt(2Rh-h^2)}

V=Tank volume
L= Tank length
R= Tank radius
h= Distance from top of tank to surface of liquid

What I want to do is to rearrange the above equation so that h is the subject. can this be done?