## sandy524 3 years ago Find the derivative of f when f(x) = 2 tan(x) + 3 cot(x)

1. cwrw238

derivative of tan x is sec^x can't remember derivative of cot x - try googling it first term of derivative is 2 sec^2 x

2. sandy524

of cotx? its -csc^2

3. cwrw238

4. sandy524

sol: let y=f(x) y=2tan(x)+3cot(x) =2dy/dxtanx+3dy/dxcotx =2*sec^2x+3*-cosec^2x =2sec^2x-3cosec^2x

6. cwrw238

oh ok so f'(x) = 2 sec^2 x - 3 csc^2 x

7. sandy524

think they want me to make in ration form its number 3 on the hw i have attached

9. sandy524

thats not one of the answer choices

10. sandy524

11. sandy524

are these questions???

13. sandy524

yes the document i have attached is the homework i am looking at number 3 specifically

14. cwrw238

ah what they have done is convert the sec and csc to sin and cos

15. sandy524

okay...

16. sandy524

17. cwrw238

2 sec^2 x - 3 csc^2 x = 2 * 1/cos^2 x - 3 * 1 / sin^2 x

18. cwrw238

|dw:1350060084696:dw|

19. sandy524

20. sandy524

21. sandy524

i have to turn it on in ten minutes

22. cwrw238

well i think it is the answer but its in different form to your choices - i'm trying to figure it out

23. swissgirl

2sec^2(x)-3csc^2(x)?

24. cwrw238

yes - do you agree with that answer?

25. sandy524

the answer choices r on the document

26. sandy524

27. sandy524

have attached the hw

28. sandy524

the answer choice are on the paper

29. cwrw238

i know that sandy - but i can't figure out which is equivalent to the sec and csc expression

30. swissgirl

hmm maybe you need to get a common deonmanator

31. sandy524

:(

32. sandy524

33. sandy524

34. sandy524

due in four minutes

35. sandy524

36. sandy524

i dont need an explainatio just the answer

37. sandy524

nvm the hw is past due now :(

38. cwrw238

there might be a mistake in the paper i'm sure 2sec^2x - 3 csc^2 x is correct but u need to convert it

39. sandy524

smh wow

40. cwrw238

hold on - i think I've got it

41. sandy524

its too late

42. sandy524

thank u anyways

43. swissgirl

ohhh I got the answer $$\large {2-5\cos^2(x) \over \sin^2(x)\cos^2(x)}$$

44. cwrw238

yes - i've converted the to sines and cosines but i can't get any of the choices on the paper yes - i got that - but its not one of the choices

45. swissgirl

its the fourth choice

46. cwrw238

oh - i've been looking in the wrong place!!!!!

47. swissgirl

hahah I know its quite confusing to follow

48. cwrw238

lol