6. Harmonic functions: Check that the following functions are harmonic. If yes, find their harmonic conjugates using the analytic continuation. (a) u=x+2x-3x²+1 (b) ue sinx (c) u=x³+y³. • Find an analytic function f(z) such that its real part is u(x,y) = sin x cosh y . Let v be a harmonic conjugate of u. Show that gu²² is a harmonic function.