## sat_chen Group Title integral subsitution confused one year ago one year ago

1. sat_chen Group Title

|dw:1359530329483:dw|

2. sat_chen Group Title

|dw:1359530356277:dw|

3. sat_chen Group Title

|dw:1359530523166:dw|

4. sat_chen Group Title

what the heck do you do after this

5. dumbcow Group Title

are those 9's inside radical ?

6. sat_chen Group Title

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

7. sat_chen Group Title

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

8. sat_chen Group Title

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

9. sat_chen Group Title

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 Group Title

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. sat_chen Group Title

so you wouldd ger 3x +7 /7 ?

12. sat_chen Group Title

for sec

13. dumbcow Group Title

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

14. sat_chen Group Title

oh right right silly me

15. sat_chen Group Title

|dw:1359532127694:dw|

16. sat_chen Group Title

is that it?

17. dumbcow Group Title

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

18. sat_chen Group Title

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

19. dumbcow Group Title

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

20. sat_chen Group Title

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

21. dumbcow Group Title

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

22. sat_chen Group Title

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

23. sat_chen Group Title

u in us too?

24. dumbcow Group Title

yeah about 1 am here in AZ (best state)

25. sat_chen Group Title

and dont use wolfram like to get these things down myself

26. sat_chen Group Title

u in college?

27. sat_chen Group Title

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

28. dumbcow Group Title

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

29. sat_chen Group Title

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

30. dumbcow Group Title

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

31. sat_chen Group Title

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

32. dumbcow Group Title

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

33. dumbcow Group Title

bye

34. sat_chen Group Title

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