# Toronto Math Forum

## APM346-2016F => APM346--Lectures => Chapter 9 => Topic started by: Shentao YANG on November 19, 2016, 10:05:43 PM

Title: Are these typos?
Post by: Shentao YANG on November 19, 2016, 10:05:43 PM
http://www.math.toronto.edu/courses/apm346h1/20169/PDE-textbook/Chapter9/S9.1.html#mjx-eqn-eq-9.1.15
I think the coefficient for last term should be ${1 \over {2\pi c}}$ instead of ${1 \over {4\pi c}}$.

http://www.math.toronto.edu/courses/apm346h1/20169/PDE-textbook/Chapter9/S9.1.html#mjx-eqn-eq-9.1.19
I think this equation should be $(\Delta + {{{\omega ^2}} \over {{c^2}}})v = {1 \over {{c^2}}}f(x)$ instead of  $(\Delta + {{{\omega ^2}} \over {{c^2}}})v = f(x)$
Title: Re: Are these typos?
Post by: Victor Ivrii on November 20, 2016, 10:35:52 AM
1) Yes, it is typo. Corrected

2) No, since the wave equation is in the form
$$\Delta u - c^{-2}u_{tt}= fe^{i\omega t}.$$