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Mathematics 19 Online
OpenStudy (unklerhaukus):

\[\int\cot (x)\cdot\text dx\]

OpenStudy (unklerhaukus):

what is the easy way to do this?

mathslover (mathslover):

put cot x = cos x/ sin x

mathslover (mathslover):

yes please wait

OpenStudy (unklerhaukus):

\[\int\frac{\cos x}{\sin x}\text dx\]

OpenStudy (anonymous):

\[\ln \left| \sin(x)\right|\]

OpenStudy (anonymous):

+C !

mathslover (mathslover):

\[\large{\int{\frac{cosx}{sinx}}dx}\] \[\large{du = cos(x)dx}\] right?

OpenStudy (unklerhaukus):

oh yeah,

mathslover (mathslover):

du = cos(x) and sin (x) = u

mathslover (mathslover):

\[\large{\int{\frac{cosx}{sinx}}=\int{\frac{du}{u}}}\] Can u solve this integral now?

mathslover (mathslover):

You will get : \(\large{ln|u| +C}\)

mathslover (mathslover):

u = sin x

OpenStudy (unklerhaukus):

\[\int \cot x \text dx \]\[=\int\frac{\cos x}{\sin x}\text dx\] \(u=\sin (x)\) \(\text du = \cos(x)\text dx\) \[=\int\frac{\text du}u\]\[=\ln |u|+c\]\[=\ln |\sin x|+c\]

mathslover (mathslover):

good work .. you got it @UnkleRhaukus

OpenStudy (anonymous):

you are not familiar with this ?! \[\int\limits_{}^{}\frac{u'(x)}{u(x)}dx = \ln(\left| u(x) \right|+C\]

mathslover (mathslover):

Great!!! ..

OpenStudy (unklerhaukus):

thanks mathslover

mathslover (mathslover):

@Neemo being familiar with that and being familiar with the proof are diff. things :)

OpenStudy (unklerhaukus):

yeah it makes sense now it just wasn't an obvious substitution

mathslover (mathslover):

best of luck .. have to go now bbye thanks!!

OpenStudy (unklerhaukus):

thank you

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