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### Simplifying and Solving a Natural Log Problem

```
Date: 11/15/95 at 12:40:58
From: Anonymous
Subject: integration of ln(r/a)dr

Integrate ln(r/a)dr -- the limits are a to b.  Is this possible, or is there
some table for this??  Thanx.
```

```
Date: 12/14/95 at 22:10:23
From: Doctor Ken
Subject: Re: integration of ln(r/a)dr

Hello!

The first thing I think I'd do is to simplify the problem a little bit.
You can actually make the "a" not matter so much in this problem by
noticing that ln(r/a) = ln(r) - ln(a), and ln(a) is just a constant.
Then you can apply the antiderivative of Natural Log: it's r*ln(r) - r.

Good luck!

-Doctor Ken,  The Geometry Forum

```
Associated Topics:
High School Calculus

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