## anonymous 5 years ago can someone walk me through the final step of trig substitution?

1. anonymous

calc?

2. anonymous

as in the step where you take the sin(theta) or whatever trig you're using and apply it to a triangle

3. anonymous

yep. calc2

4. anonymous

sorry, brb

5. anonymous

How about giving us the question, or at least how far you are?

6. anonymous

$\int\limits \sqrt{25x^2-4}/x dx$

7. anonymous

and i'm looking for how to to use a triangle to do the final substitution

8. anonymous

let x=5 tan theta

9. anonymous

scratch that x=5 sec theta. Is this what you are looking for or are you at another part of the problem?

10. anonymous

Scratch that x=2 sec theta. Sorry the 25 distracted me.

11. anonymous

the very end. after the trig has been integrated, and you go to substitute variables back in for theta

12. anonymous

after integration i have 2(tan(theta)-theta)

13. anonymous

Draw a triangle and put your stuff on a triangle. It is difficult to guide you in the middle of a problem and we don't know the work. Watch this tape. I watch it every time I have to do a trig sub. http://www.youtube.com/watch?v=CXKoCMVqM9s&feature=BFa&list=PL590CCC2BC5AF3BC1&index=25

14. anonymous

ah that should work. thanks