1. The problem statement, all variables and given/known data Solve ut=kuxx u(x,0)=0 (ψ(x)) u(0,t)=1 on the half line 0<x<infinity (exercise 2, 3.1, Strauss) 2. Relevant equations 3. The attempt at a solution There are two bits I don't get: First, I know I have to make an odd or even extension to the whole line. But for both even and odd extensions, the formulae are: u(x,t)=1/(√4∏kt)(∫(e-(x-y)2/4kt±e-(x+y)2/4kt)ψ(y)dy) this means for u(x,0)=0, everything is multiplied by 0, which clearly isn't right. Second, I don't know which extension to apply, it seems like both should work: I can either make an odd extension about the line x=1 or an even extension about the t axis, both will intercept the t axis at 1, hence satisfying the BC. Any help would be greatly appreciated!