# Definite integral with x^2+c in the denominator

1. Jan 30, 2014

### Hypatio

1. The problem statement, all variables and given/known data

2. Relevant equations

solve the definite integral

$$\int_{2.6}^{5.5} \frac{1}{x^2+9}dx$$

3. The attempt at a solution

ln(5.5^2+9)-ln(2.6^2+9) doesn't seem correct

2. Jan 30, 2014

### king vitamin

Can you show your steps in getting that solution? What did you get for the antiderivative of the integrand?

3. Jan 30, 2014

### Dick

If you take the derivative of log(x^2+9) you will not get 1/(x^2+9) (at least if you don't forget the chain rule). You need a trig substitution to do that integral.