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## anonymous 3 years ago integral subsitution confused

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1. anonymous

|dw:1359530329483:dw|

2. anonymous

|dw:1359530356277:dw|

3. anonymous

|dw:1359530523166:dw|

4. anonymous

what the heck do you do after this

5. dumbcow

are those 9's inside radical ?

6. anonymous

you dont have to write the whole steps like last time can you just give me advice and yes they are

7. anonymous

and you can just make them easy by making them into (3/7x)^2

8. anonymous

|dw:1359530730683:dw| (3/7x)^2 something like that for the bottom part

9. anonymous

when you do it can you confirm that you get the same solution as in my solving part and help me from there on. thanks

10. dumbcow

ok i get same solution (i simplified the constants) $\frac{343}{81}(\frac{\sec^{3} \theta}{3} - \sec \theta) +C$ now you have to substitute back in "x" $\tan \theta = \frac{3x}{7}$ and $\sec^{2} \theta = \tan^{2} +1 = \frac{9x^{2}}{49} +1 = \frac{9x^{2} +49}{49}$ take sqrt to get "sec" , then cube that to get sec^3

11. anonymous

so you wouldd ger 3x +7 /7 ?

12. anonymous

for sec

13. dumbcow

no it would be ... sqrt(9x^2 +49) /7 because of addition inside you can't just take sqrt of each term

14. anonymous

oh right right silly me

15. anonymous

|dw:1359532127694:dw|

16. anonymous

is that it?

17. dumbcow

yep ... oh dont forget the 3 in denominator probably need to s.continue to simplify

18. anonymous

but hold on my angles look like this |dw:1359532285169:dw|

19. dumbcow

hmm hypotenuse should be .... sqrt(9x^2 +49)

20. anonymous

oh f i see why i forgot to square. its 2am and i had a long day -.-

21. dumbcow

haha time to get some sleep ....have wolfram do work for you

22. anonymous

yep just finished it got the right answer thanks a lot time for bed i cant even think straight right now

23. anonymous

u in us too?

24. dumbcow

yeah about 1 am here in AZ (best state)

25. anonymous

and dont use wolfram like to get these things down myself

26. anonymous

u in college?

27. anonymous

taking engineering math not my strongest subject but where the jobs go i go XD

28. dumbcow

nope... finished with college , i work as a math tutor so i come on here to practice and help people

29. anonymous

hmm so you planning to be a teacher you would be a good one

30. dumbcow

engineering is great field but tough classes have to take quite a bit of math

31. anonymous

yep still got to diff linear algebra etc good night bed is calling for me :P

32. dumbcow

i qualified to be a teacher but am undecided .... i prefer tutoring 1 on 1 ..... classroom teaching isn't my style

33. dumbcow

bye

34. anonymous

you would be a great 1 v1 tutor too yea good night

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