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Mathematics 12 Online
OpenStudy (anonymous):

integration of cosx/xsinx+cosx

zepdrix (zepdrix):

Like this?\[\Large \int\limits \frac{\cos x}{x \sin x + \cos x}dx\]+_+

zepdrix (zepdrix):

\[\Large \int\limits \frac{\cos x}{x \sin x}+ \cos x\;dx\]Orrr this maybe? +_+

OpenStudy (anonymous):

yeah!!.. the earlier one

zepdrix (zepdrix):

Hmmmmmm

zepdrix (zepdrix):

Seems like a u-sub gets us close, but not close enough D:\[\Large u=x \sin x+\cos x\]\[\Large du=\cancel{\sin x}+x \cos x -\cancel{\sin x} \; dx\]\[\Large \frac{1}{x}du=\cos x\; dx\] Giving us,\[\large \int\limits \frac{1}{x \sin x+\cos x}(\cos x dx) \quad=\quad \int\limits \frac{1}{u}\left(\frac{1}{x}du\right)\]

zepdrix (zepdrix):

Are you sure I wrote the problem out correctly? :o What types of methods have you learned for solving these?

OpenStudy (anonymous):

well.. i'm not good at u-substitution!!.. methods i know are: ntegration by parts partial fractions trig substitution rationalizing substitutions and yeah you wrote the problem correct enough :P >_<

OpenStudy (anonymous):

hmmm

zepdrix (zepdrix):

@amistre64 @hartnn Bah I'm tired :c gotta get to bed. Maybe one of these smart fellas can help ya.

OpenStudy (anonymous):

hahaha!!.. sure!!.. thanks for your help!!.. sleep well chap!! . .

OpenStudy (anonymous):

the denominator is a differential d(x*sin(x))

OpenStudy (anonymous):

i think that is a clue.

OpenStudy (anonymous):

this is going to have me up all night.

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