evaluate the integral

• June 19th 2009, 09:22 PM
jackm7
evaluate the integral
Here is the integral: sqrt[x^2 - 9]/x^2.

I know the answer (ln (x + sqrt[x^2+9]) - (sqrt[x^2 - 9]/x))

How does this answer come about? I have tried using the trig functions and I am getting no where close to the answer.

Cheers!
• June 19th 2009, 09:27 PM
malaygoel
have you tried $x=3sec\theta$