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Integral of 20 sec³(x) dx

dexstarr

New member
Jun 12, 2013
4
I'm having a hard time breaking this down using tri identities.

} = integral sign


20}sec^3(x) dx
20}sec^2(x) * sec(x) dx
20}[tan^2(x)-1] * sec(x) dx

after this I'm stuck. I tried letting u = tan(x) or sec(x) but i cant seem to cancel anything out.
 

SuperSonic4

Well-known member
MHB Math Helper
Mar 1, 2012
249
Re: Integral of 20 sec^3(x)dx

I'm having a hard time breaking this down using tri identities.

} = integral sign


20}sec^3(x) dx
20}sec^2(x) * sec(x) dx
20}[tan^2(x)-1] * sec(x) dx

after this I'm stuck. I tried letting u = tan(x) or sec(x) but i cant seem to cancel anything out.
\(\displaystyle 20 \int \frac{1}{\cos^3(x)}\)

Multiply by \(\displaystyle \dfrac{\cos(x)}{\cos(x)}\)

\(\displaystyle 20 \int \frac{\cos(x)}{\cos^4(x)}\)

\(\displaystyle 20 \int \frac{\cos(x)}{(1-\sin^2(x))^2}\)

Now use \(\displaystyle u = \sin(x)\)
 

topsquark

Well-known member
MHB Math Helper
Aug 30, 2012
1,143