# Homework Help: I don't like memorizing

1. Feb 26, 2009

### orthovector

does anybody know how to derive this integral???

$$\int \frac{dx}_{\sqrt{x^2 + a^2}}$$ $$= ln(x+ \sqrt{x^2 + a^2})$$

Last edited: Feb 26, 2009
2. Feb 26, 2009

### Dick

Looks like you already took it, wrongly. Looks more to me like an arctan. Some things are worth memorizing. Not all, but some.

3. Feb 26, 2009