- #1

ShayanJ

Gold Member

- 2,797

- 602

But is it possible to find a set of functions ## \phi_n(x,y) ## such that you can write for an arbitrary function of x and y ## f(x,y)=\sum_n c_n \phi_n(x,y) ##? Is there any orthonormality relation that lets you find the coefficients?

Thanks