Ask your own question, for FREE!
Mathematics 21 Online
OpenStudy (studygurl14):

@satellite73 @solomonzelman

OpenStudy (studygurl14):

OpenStudy (studygurl14):

@SolomonZelman @jim_thompson5910

OpenStudy (solomonzelman):

\(\color{#000000}{ \displaystyle \int \frac{1+\cos x}{\sin x} dx }\) \(\color{#000000}{ \displaystyle \int \frac{1}{\sin x} dx +\int \frac{\cos x}{\sin x} dx }\) or do you want an easier approach?

OpenStudy (studygurl14):

you don't get a notification unless you post...which you just did lol @chosenmatt

OpenStudy (studygurl14):

Whatever works is fine.

OpenStudy (solomonzelman):

Yeah, the integral for csc(x), and for tan(x)....

OpenStudy (studygurl14):

oh, duh

jimthompson5910 (jim_thompson5910):

cos/sin = cot, not tan

OpenStudy (solomonzelman):

yes, thanks jim. What the hack am I saying? :)

OpenStudy (studygurl14):

wait, I don't know the integral for csc and cot...?

OpenStudy (studygurl14):

My book only has for csc^2

OpenStudy (solomonzelman):

We can proof the formulas for them, or you can just use the formula for them/

OpenStudy (solomonzelman):

it is just the matter of willingness.

OpenStudy (studygurl14):

since I have to get my homework done soon, I'm gonna go with formula. Then, after, you can show proof

OpenStudy (anonymous):

if it was me, i would look in the back of the book almost all of calc 2 is right there on two pages

OpenStudy (solomonzelman):

If it was me, I would just use mathematica))

OpenStudy (anonymous):

lol or wolframalpha (in the browser already)

OpenStudy (studygurl14):

the book says the integral of cot is ln|sin x| + C

OpenStudy (studygurl14):

I checked the back

OpenStudy (anonymous):

that one is a simple u - sub

OpenStudy (studygurl14):

oh, right

OpenStudy (anonymous):

it is \[\int \csc(x)dx\] you need to look up

OpenStudy (studygurl14):

ok

OpenStudy (studygurl14):

-ln|csc x - cot x| + C

OpenStudy (studygurl14):

Is that right?

OpenStudy (solomonzelman):

\(\color{#000000}{ \displaystyle \int \frac{1+\cos x}{\sin x} dx }\) \(\color{#000000}{ \displaystyle \int \frac{2+e^{ix}+e^{-ix}}{e^{ix}-e^{-ix}} dx }\) yeah, either way you end up with the same thing, although in a bit different form:)

OpenStudy (daniel.ohearn1):

You are right about the ln

OpenStudy (anonymous):

got my book right here, let me check

OpenStudy (daniel.ohearn1):

You can get that by multiplying the numberator and denominator by csc+cotx and negating the top to get integral of -1/u form

OpenStudy (daniel.ohearn1):

Integral of cot(x)dx is simplier.

OpenStudy (anonymous):

my book does not have the minus sign

OpenStudy (studygurl14):

weird? mine does...?

OpenStudy (anonymous):

\[\ln(\csc(x)-\cot(x))\]

OpenStudy (studygurl14):

maybe it doesn't matter...?

OpenStudy (anonymous):

possible we can check by differentiation

OpenStudy (studygurl14):

Idk why I even have to use that formula when I haven't even learned it yet

OpenStudy (daniel.ohearn1):

It does and there should be a minus

OpenStudy (anonymous):

that is the point of a formula you don't have to learn it, just look it up

OpenStudy (daniel.ohearn1):

-ln abs(cotx+cscx)

OpenStudy (anonymous):

maybe my Stewart has a typo i think he just passed away

OpenStudy (daniel.ohearn1):

Why it's important to recognize the steps needed for that result

OpenStudy (anonymous):

\[\log(\csc(x)-\cot(x))\] is definitely right just check it

OpenStudy (studygurl14):

??

OpenStudy (daniel.ohearn1):

multiply cscxdx by cotxcscx / cotxcscx you get csc^2+cotxcscx / cotx+cscx yeah?

OpenStudy (daniel.ohearn1):

right?

OpenStudy (solomonzelman):

The first time I integrated \(\csc x\) in my life, I remember, I ended up with. \(\color{#000000}{ \displaystyle \int\frac{1}{\sin x}dx =\int\frac{\sin x}{1-\cos^2x}dx }\) Sub, \(u=\cos x\) \(du=-\sin x dx\) \(\color{#000000}{ \displaystyle -\int\frac{1}{1-u^2}du=\int\frac{1}{u^2-1}du }\) Partial Fractions, \(\displaystyle \frac{1}{u^2-1}=\frac{A}{u+1}-\frac{B}{u-1}\) \(\displaystyle 1=A(u-1)-B(u+1)\) \(\displaystyle B=-1/2\) \(\displaystyle A=1/2\) \(\color{#000000}{ \displaystyle \int\frac{1}{u^2-1}du=\int\frac{1/2}{u+1}du-\int\frac{1/2}{u-1}du = }\) \(\color{#000000}{ \displaystyle \frac{1}{2}\ln(\sin x+1)-\frac{1}{2}\ln(\sin x-1) = }\) \(\color{#000000}{ \displaystyle \frac{1}{2}\ln\left(\frac{\sin x+1}{\sin x-1}\right)+C }\)

OpenStudy (solomonzelman):

it is not very hard to proof these, just using u-substitution and an algebraic technique of partial fractions.

OpenStudy (solomonzelman):

Oh, I left of absolute value. Sorry.

OpenStudy (solomonzelman):

Good luck with integration:)

OpenStudy (daniel.ohearn1):

And it u=cosx so your answer should involve cosine

OpenStudy (studygurl14):

Is the answer ln|1-cos x| + c?

OpenStudy (solomonzelman):

Yes, cosine instead of sine....

OpenStudy (solomonzelman):

I overworked myself. gtg

OpenStudy (studygurl14):

lol, thanks

OpenStudy (daniel.ohearn1):

\[\int\limits cscx dx = \int\limits - (-\csc^2(x)-\cot(x)\csc(x))/\cot(x)+\csc(x) = \int\limits \frac{- 1 }{ u}du= -\ln \left| \cot(x) +\csc(x) \right| +C\]

OpenStudy (daniel.ohearn1):

u= cot(x) + csc(x) du= -csc^2(x) - csc(x)cot(x)

OpenStudy (daniel.ohearn1):

So hopefully this convinces you that -ln... is the solution

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!