ClearAll["Global`*"]

2D Steady Heat Equation in a plate

In class, we solved this problem by hand. As a reminder, the problem statement was:
(Subscript[L, 1]), (Subscript[L, 2]), (Subscript[T, cold]), and (Subscript[T, hot]) are all known quantities.

Θ[x_,y_]=((1-y)/2)+ (∑_(n=1)^50)((-4)/((((2n-1))^2) (π^2)))((Sinh[(2 n - 1) π (1-y) ])/(Sinh[(2 n - 1) π  ]))  Cos[(2 n - 1) π x];
ContourPlot[Θ[x,y],{x,0,1},{y,0,1},Contours->30,ColorFunction->"Rainbow"]
Plot3D[Θ[x,y],{x,0,1},{y,0,1},ColorFunction->"Rainbow"]