Hi all, I'm a final year acoustics student in the UK attempting to model the modal response of a circular plate as part of my thesis. Essentially, i have this equation : and im trying to deal with the left term of the LHS. I'm trying to find out whether the full version of the biharmonic laplacian Jm(..)cos(..) can be expanded and factorised to be in terms of Jm(..) x cos(..) x (everythingelse!) as i am trying to solve the above equation for Amn In this form my theory will work but the actual derivation of the biharmonic laplacian using trigonometric functions and bessel functions together is killing me, ive already wasted a good 2 weeks trying this! Can anyone help?