# Math Help - integration help please!!!

a definite integral, lower limit is 1, upper limit is the squre root of 3, integral is
arctan(1/x) I know how to take the integral of arctan(x), but have no clue how I should go about doing this one, help?

2. Originally Posted by pcgamer03
a definite integral, lower limit is 1, upper limit is the squre root of 3, integral is
arctan(1/x) I know how to take the integral of arctan(x), but have no clue how I should go about doing this one, help?
do integration by parts. $\arctan \frac 1x$ is the part you differentiate. i think that should work

you may want to make a substitution of u = 1/x first, but it should work without doing that

3. what do i let u equal and what do i let dv equal, thats what i am having trouble with

4. Originally Posted by pcgamer03
what do i let u equal and what do i let dv equal, thats what i am having trouble with
u = arctan(1/x), dv = 1

5. what is the derivative of arctan?

6. Ohh man, then integrating will be kinda hard for ya.

I suggest you to brush up some of derivatives, after that see integration.

7. Originally Posted by pcgamer03
what is the derivative of arctan?
that is not a question you should be asking, for the following reasons:

(1) it is something you should know by heart

(2) if you don't know it by heart, it is a very quick google search, text-page flip, or notebook-page flip away

nevertheless, i shall oblige you...

$\frac d{dx} \arctan u = \frac {u'}{1 + u^2}$ .......where $u$ is a function of $x$, of course

8. $\tan^{-1} \frac{1}{x} = \frac{\pi}{2}\cdot \frac{x}{|x|}- \tan^{-1} x$

9. Originally Posted by Krizalid
Ohh man, then integrating will be kinda hard for ya.

I suggest you to brush up some of derivatives, after that see integration.
It's interesting to look at the sequence of posts:

Originally Posted by pcgamer03
a definite integral, lower limit is 1, upper limit is the squre root of 3, integral is
arctan(1/x) I know how to take the integral of arctan(x), but have no clue how I should go about doing this one, help?
Originally Posted by pcgamer03
what do i let u equal and what do i let dv equal, thats what i am having trouble with
Originally Posted by pcgamer03
what is the derivative of arctan?
Is it just me or is the first logically inconsistent with the second and third?

10. Originally Posted by mr fantastic
It's interesting to look at the sequence of posts:

Is it just me or is the first logically inconsistent with the second and third?
i see what you are saying (if the poster was honest in the first post--about being able to find the integral of arctan(x), he would already know the answer to his/her two later posts), but i just let it slide