## ana321 2 years ago i need help

1. Trustted

help in wat

2. ana321

use half angle formulas to rewrite $\sqrt{1-\cos30 degrees/2}$

3. dumbcow

$\sin (\theta/2) = \sqrt{(1-\cos \theta)/2}$

4. ana321

using that formula o but..

5. dumbcow

so you can rewrite it as sin(15)

6. ana321

hwo do i get there i cantsee

7. dumbcow

??

8. ana321

what i mean the answer of the problem i sin 15 how do i get there id ont understand

9. dumbcow

theta = 30 so theta/2 = 30/2 = 15

10. ana321

can u show that

11. dumbcow

show what...prove that 30/2 = 15

12. ana321

no the whole process

13. dumbcow

well i looked up the half-angle identity for sin (theta/2) **shown above** it matches your expression except you have 30 degrees for the angle

14. ana321

ok ,..?

15. ana321

and

16. ana321

ok

17. ana321

nee help trig= rewrite this using half angle formula sqrt{1= \cos 135 degress/2}\]

18. dumbcow

is that a plus or minus ?

19. ana321

sorry let me rewrite it

20. ana321

$rewrtite using half aangle formulas \sqrt{1+ \cos 135 dgrees/2}$

21. dumbcow

plus means its the cosine half angle formula take the given angle --> 135 divide it by 2 --> 135/2 = 67.5 answer = cos(67.5)

22. ana321

so that my asnwer my teacher doesn tlike decimals

23. dumbcow

then write it as a fraction...the main thing is do you get the concept? find appropriate formula , then take half the angle

24. ana321

hello?

25. ana321

can u show me thewhole process and ow do is hwo it in fraction

26. ana321

hello

27. ana321

what wre u gonnaa say

28. dumbcow

are you serious...i showed you step by step...there is no other process you should have a reference in your book or notes showing the half-angle formulas the fraction would simply be 135/2 http://www.freemathhelp.com/trig-double-angles.html

29. ana321

need help trig rewrite using half angle idnetities =1-cos210 degress/sin210 degrees

30. ana321

need help trig rewrite using half angle idnetities =1-cos210 degress/sin210 degrees

31. ana321

heloo

32. dumbcow

$\rightarrow \frac{1-\cos 210}{\sin 210}$

33. ana321

yes i know the formula i dont know how to use it

34. dumbcow

please don;t message me the same thing you are posting, thanks and this is different it isn't any of the half-angle formulas

35. ana321

no yes

36. dumbcow

$\frac{1-\cos 210}{\sin 210} = \csc 210 - \cot 210$ not sure how else to rewrite it unless you want to use sum/difference formulas

37. ana321

ok tanks

38. ana321

s o how do i ewrite using half angle idnetities =1-cos210 degress/sin210 degrees

39. ana321

by just saying it equals to 1-cos theta/sin theta

40. ana321

???

41. dumbcow

umm i already answered you before regarding this question

42. ana321

no i dont grasp it

43. dumbcow

i don't think you can rewrite using half-angle formulas look for yourself...see that the expression does not match any the formulas

44. ana321

its what it says n my book

45. ana321

yes it does tan theta /2

46. ana321

hello

47. dumbcow

yes i am wrong...my ref sheet has a different but equivalent formula for tangent sorry...hey i learned something anyway, now just take half the angle