# Question: a function fxy is called harmonic is it fulfills the...

###### Question details

A function f(x,y) is called harmonic is it fulfills
the laplace equation.

a) Show by using the chain rule that

if

where a and b are constants.

b) Use a) to show that the function e^(2x+3y) *sin(3x-2y) is
harmonic.

c)Show that the product of two harmonic functions is harmonic if
their gradients is perpendicular to each other at each point.

Please explain thoroughly. :)

Thank you in advance. :)