# Math Help - trigonometric integral

1. ## trigonometric integral

how to solve this integral
dt/(cost)^3
?

2. Originally Posted by transgalactic
how to solve this integral
dt/(cost)^3
?
See here: integrate 1&#47;&#40;Cos&#91;x&#93;&#41;&#94;3 - Wolfram|Alpha

Click on Show steps. The reduction formula can be found using integration by parts.

3. how to solve it by parts??
what parts
?

4. Originally Posted by transgalactic
how to solve it by parts??
what parts
?

(But surely you have been taught the technique ....?!)

5. yes i hav been taught but i cant see how to apply it here
so it will be effective

6. Originally Posted by transgalactic
yes i hav been taught but i cant see how to apply it here
so it will be effective
Have you even tried ....?

u = sec(x) => du = ....
dv = sec^2(x) dx => v = ......

You get I = ..... + int( ......) dx = ....... - I + int sec(x) dx => first step from Wolframalpha.

All the .....'s are things you need to fill in.