3.1 equation 12

[Bruce Wu]

http://www.math.toronto.edu/courses/apm346h1/20159/PDE-textbook/Chapter3/S3.1.html#mjx-eqn-eq-3.1.12

I might be wrong, but based on the definition of the error function given, shouldn't it be equal to $$\frac{1}{4}+\frac{1}{4}erf\left(\frac{x}{\sqrt{4kt}}\right)$$?

[Emily Deibert]

Shouldn't there also be a $\frac{1}{2}$ as part of $U(x,t)$? Or else where does the extra term of $\frac{1}{2}$ come from?