# Toronto Math Forum

## MAT244-2014F => MAT244 Math--Lectures => Topic started by: Min Zhang on September 23, 2014, 06:32:35 PM

Title: Questions about Section 1.2 on page 11
Post by: Min Zhang on September 23, 2014, 06:32:35 PM
I have been reading the textbook and found the following part that I don't quite understand:

At the top of page 11, it says

Quote
By the chain rule the left side of Eq. (6) is the derivative of ln|p-900| with respect to t, so we have  $d/dt\ ln|p-900| = 1/2$.

Then, by integrating both sides of Eq. (7), we obtain  $\ln|p-900| = t/2+C$

So my questions are:

1. Why can we get those statements?

2. Why do we have to insert a constant number $C$?

Thank you very much!
Title: Re: Questions about Section 1.2 on page 11
Post by: Victor Ivrii on September 23, 2014, 11:24:06 PM
In virtue of elementary knowledge of Calculus I.