# trigonometric integral

• Apr 15th 2011, 01:06 AM
transgalactic
trigonometric integral
how to solve this integral
dt/(cost)^3
?
• Apr 15th 2011, 01:12 AM
mr fantastic
Quote:

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.
• Apr 15th 2011, 01:24 AM
transgalactic
how to solve it by parts??
what parts
?
• Apr 15th 2011, 01:28 AM
mr fantastic
Quote:

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

Use Google: Integration by parts.

(But surely you have been taught the technique ....?!)
• Apr 15th 2011, 01:43 AM
transgalactic
yes i hav been taught but i cant see how to apply it here
so it will be effective
• Apr 15th 2011, 02:01 AM
mr fantastic
Quote:

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.