## krypton Group Title y=d/dx integralcosx to 0 t/(1+t)dt one year ago one year ago

1. krypton Group Title

$d/dx \int\limits_{0}^{cosx} \frac{ t }{ 1+t } dt$

2. Outkast3r09 Group Title

$\frac{cosx}{1+cosx}$

3. krypton Group Title

how did u do it?

4. Zekarias Group Title

@Outkast3r09 I think u made a miss take in your first step (While u made the integral)

5. Outkast3r09 Group Title

the derivative of an integral is simply the integral itself with the variables in other words ... integrals and derivatives cancel eachother out

6. Outkast3r09 Group Title

$\frac{cosx}{1+cosx}$is your answer

7. Zekarias Group Title

It should be$\cos(x)-\ln(1+\cos(x))$

8. Outkast3r09 Group Title

|dw:1349804491261:dw|

9. Zekarias Group Title

Now take the derivative

10. Outkast3r09 Group Title

it shouldn't be anything @ zekarias

11. Outkast3r09 Group Title

@zekarias ... you don't need to do anything

12. Zekarias Group Title

What u get finally?

13. krypton Group Title

so the answer is just cosx/1+cosx ?

14. Outkast3r09 Group Title

yes

15. krypton Group Title

thanks,wolfram gives me the same answer,just wanted to make sure how it was done

16. Outkast3r09 Group Title

it's just simply knowing how an integral work... there is a lot of work to do it zekarias way but if you just know that the the derivative on an integral will bring you back to the f(x) within the integral... that's all you need to know(This works anytime the lower limit is some real number) because if you think about it.... |dw:1349804918350:dw| if you take the derivative of f(n)... you'll always get zero

17. krypton Group Title

oh thanks alot sweedy :)