reeny1996 2 years ago if F(x)=tanx, then fprime(pi/6)=

Have you differentiated F(x) and then sub'ed $$\frac{\pi}{6}$$ into it?

2. waterineyes

Do you know the derivative of tan(x) ??

3. reeny1996

i kno the differvative is secxtanx but i dont know where to go frm there :/

4. waterineyes

Yes, than just replace x by pi/6..

5. reeny1996

(2$\sqrt{3}$/3 and $\sqrt{3}$/3

6. waterineyes

$F'(\frac{\pi}{6}) = \sec(\frac{\pi}{6}) \cdot \tan(\frac{\pi}{6})$

7. reeny1996

igot tht part

8. waterineyes

What is the value of : $\sec (\frac{\pi}{6})$

9. reeny1996

2root3/3

10. waterineyes

Yes and what is for tan(pi/6) = ??

11. reeny1996

root3/3

12. waterineyes

Wait, derivative of tan(x) isn't it sec^2(x) ??

13. reeny1996

its not ?

14. waterineyes

$\frac{d}{dx} \tan(x) = \sec^2(x)$

15. reeny1996

thts y im getting the wrong answer

16. reeny1996

thank you

17. waterineyes

You were doing the derivative of sec(x)..

18. reeny1996

yea

19. waterineyes

$\frac{d}{dx}\sec(x) = \sec(x) \cdot \tan(x)$ It is okay and sorry from my side too, I also got confused.. And you are welcome dear..

20. reeny1996

ok idk how to combine the 2 radicals

21. waterineyes

Where ??

22. reeny1996

sec^2

23. waterineyes

$F'(\frac{\pi}{6}) = \sec^2(\frac{\pi}{6})$

24. reeny1996

yea

25. reeny1996

|dw:1352970940060:dw|

26. waterineyes

$\implies \frac{2 \sqrt{3}}{3} \times \frac{2\sqrt{3}}{3} \implies ??$

27. waterineyes

This is simple multiplication and division now...

28. reeny1996

i know but im not getting the right answer

29. reeny1996

4

30. waterineyes

What are you getting tell me first...

31. waterineyes

Its not 4... You are missing something.

32. waterineyes

$\sqrt{3} \times \sqrt{3} = ??$

33. reeny1996

2 times 2=4 root3 times root 3= 3 4 times 3 =12 12 divide3 =4

34. waterineyes

12 divided by 3 ??? Are you sure in denominator it is 3 ??

35. reeny1996

im not too good with my unit circle

36. waterineyes

Dear, what will you get when you will square 3 ??

37. reeny1996

9

38. waterineyes

Check the colored things here : $\frac{2 \sqrt{3}}{\color{red}{3}} \times \frac{2 \sqrt{3}}{\color{red}{3}} = ??$

39. reeny1996

9

40. waterineyes

Yes it is 12 divided by 9 and not 3.. So what will you get now ??

41. reeny1996

ohhhhhh

42. reeny1996

4/3

43. reeny1996

44. reeny1996

my mistake...srry if i took up yhur time

45. waterineyes

It is okay but be careful from next time... These are called "Silly Mistakes..." Ok, now concentrate more on new problems...

46. waterineyes

It is okay..

47. reeny1996

thanks a lot :)))