# Toronto Math Forum

## APM346-2022S => APM346--Lectures & Home Assignments => Chapter 2 => Topic started by: Yifei Hu on February 19, 2022, 09:16:55 PM

Title: Text Book 2.4 Example 2.1
Post by: Yifei Hu on February 19, 2022, 09:16:55 PM
In this problem, $-1 < t < -\infty$, when applying D' Alembert's formula, why we integrate from 0 to t instead of from -1 to t?
We integrate from $t=0$ because for $t=0$ initial conditions are done. $-1<t$ is a domain where $f(x,t)$ is defined