Question

integrate dx/9+x^2

Answer 1

Isn't this inverse tangent of something?

Answer 2

\[\int\limits\frac{1}{9+x^{2}} dx\]
\[\int\limits\frac{1}{3^{2}+x^{2}} dx\]
Inverse function..

Answer 3

if you don't know how to do trig substitution integrals yet, then this is what integral tables are for
http://integral-table.com/old/IntegralTable.pdf
find the form that matches your integral

Answer 4

\[\frac{1}{a^{2}+x^{2}}= \frac{1}{a} \tan^{-1} \frac{x}{a} \]

Answer 5

^which is integral (10) in the list given