Ask your own question, for FREE!
Mathematics 15 Online
OpenStudy (studygurl14):

Calculus question. Integral and substitution @zepdrix

OpenStudy (studygurl14):

zepdrix (zepdrix):

Oh this silly problem :) lol ya i remember this

zepdrix (zepdrix):

It's good that they gave you the multiplication step, because that's not something you can easily come up with on your own. It's a messy trick to making this one work.

zepdrix (zepdrix):

\[\large\rm \int\limits \csc x\left(\frac{\csc x+\cot x}{\csc x+\cot x}\right)dx=\int\limits\frac{\csc x(\csc x+\cot x)}{\csc x+\cot x}dx\]You understand that only the numerator is getting this cscx, ya? :)

OpenStudy (studygurl14):

Is this correct? so far

zepdrix (zepdrix):

Oooo no no no, let's not do sines and cosines :OO It might be right, but uhhh boy that's a lot of extra work

OpenStudy (studygurl14):

ok, lol. What's your method?

zepdrix (zepdrix):

...

OpenStudy (studygurl14):

du = (-csc x cot x) + (sec x tan x), yes?

OpenStudy (studygurl14):

oh, then du = (-csc x cot x) + sec^2 x

OpenStudy (studygurl14):

@zepdrix is that ok?

rishavraj (rishavraj):

heck i ruined \[\csc x \times \frac{ \csc x - \cot x }{ \csc x - \cot x }\]

OpenStudy (studygurl14):

???

zepdrix (zepdrix):

Well first multiply out your numerator so you have an idea of what's going on.\[\large\rm =\int\limits \frac{\csc x \cot x+\csc^2x}{\csc x+ \cot x}dx\]What you're doing is, you're letting your denominator =u, and something magical happens :)

OpenStudy (studygurl14):

Ah, I think I see where you're getting @zepdrix

rishavraj (rishavraj):

@StudyGurl14 just an alternate method so u will have \[\int\limits\frac{ \csc x (\csc x - \cot x) }{ \csc x - \cot x } dx\]

OpenStudy (studygurl14):

du/dx = \(\Large -\csc x \cot x - (-\csc^2 x)=-\csc x \cot x + csc^2 x\)

OpenStudy (studygurl14):

Wait, hold on

OpenStudy (studygurl14):

Made a mistake there

zepdrix (zepdrix):

Woops, we're using csc x + cot x for our u, right? :O You silly billy

OpenStudy (studygurl14):

du/dx = \(\Large -\csc x \tan x + \csc^2 x\) So dx = \(\Large\frac{1}{-\csc x \tan x + \csc^2 x}\) yea?

OpenStudy (studygurl14):

tack on a du at the end

zepdrix (zepdrix):

cot x --> -csc^2x, right?

rishavraj (rishavraj):

\[\csc x - \cot x = u\] so \[du = (-\csc x \cot x + \csc^2 x) dx\]

OpenStudy (studygurl14):

ugh, I keep doing that lol. Yeah

OpenStudy (studygurl14):

So that'd be negative, then you pull out the -1, and it changes to |dw:1453498357930:dw|

Can't find your answer? Make a FREE account and ask your own questions, OR help others and earn volunteer hours!

Join our real-time social learning platform and learn together with your friends!
Can't find your answer? Make a FREE account and ask your own questions, OR help others and earn volunteer hours!

Join our real-time social learning platform and learn together with your friends!