# Toronto Math Forum

## APM346-2015F => APM346--Misc => Textbook errors => Topic started by: Bruce Wu on November 08, 2015, 12:52:15 AM

Title: Equation 6.4.12
Post by: Bruce Wu on November 08, 2015, 12:52:15 AM
http://www.math.toronto.edu/courses/apm346h1/20159/PDE-textbook/Chapter6/S6.4.html#mjx-eqn-eq-6.4.12

We are already evaluating $u$ at $r=a$. So after the summation sign it should be $a^n$ instead of $r^n$

Correct