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## anonymous 4 years ago need help im going to draw a triangle and im doing the law of sines so if anyone can help please do cuz im confused.. please click this to helpp

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1. anonymous

|dw:1335063015673:dw|

2. anonymous

Do you need to find a?

3. anonymous

so let me explain im trying to find a okay c=96.3, b=145.67 , B=39.5degrees, C=74.2degrees,

4. anonymous

law of sines is a/sinA=b/sinB

5. anonymous

Sine rule says: SinA/a = SinB/b = SinC/c

6. anonymous

okay i understand that waitt why is it sina/a instead of a/sin a

7. anonymous

SinA/a = Sin(39.5)/145.67 SinA = a*something

8. anonymous

Because they mean the same thing. A/B = C/D => B/A = D/C

9. anonymous

waitt does it even matter

10. anonymous

okay im not understanding

11. anonymous

You can find angle A by simply subtracting angles B and C from 180.

12. anonymous

okay i understand which would be 66.8

13. anonymous

Then, use this: SinA/a = Sin(39.5)/145.67 SinA = a*something SinA/something = a To find a.

14. anonymous

SinA/a = SinB/b = SinC/c IS SAME AS a/SinA = b/SinB = c/SinC

15. anonymous

but then a would be .00436

16. anonymous

I am getting 210.5

17. anonymous

That "something" in my expression is 0.00436. Divide Sin66.8 by that "something" value. Then, you get the value of a.

18. anonymous

really then let me try again...... im still not getting that are you multiplying or dividing

19. anonymous

SinA/a = Sin(39.5)/145.67 SinA = a*0.00436 a = SinA/0.00436 a = Sin66.8/0.00436 a = 210.5

20. anonymous

im not getting it first you divided than you did something else im so confused

21. anonymous

ok

22. anonymous

i also had another question

23. anonymous

Post it separately.

24. anonymous

i dont understand

25. anonymous

Which part don't you understand? :) I can help you.

26. anonymous

okay, so instead of 66.8 its 66.3

27. anonymous

im so fustrated im confusedd

28. anonymous

Punch it into the calculator and you get slightly different number from 210.5

29. anonymous

SinA/a = Sin(39.5)/145.67 SinA = a*0.00436 a = SinA/0.00436 a = Sin66.3/0.00436 a = 210

30. anonymous

i neeed helpppp

31. anonymous

i got -47.99

32. anonymous

Check your calculator first. I'm guessing you're getting different answers because your calculator is not in degree mode. That's why it's treating your angles differently.

33. anonymous

wait no i got -110.05

34. anonymous

How in the world can a length of a side of a triangle be negative? Can you show the arithmetic you used to get that number?

35. anonymous

yeppp m ycalculator wasnt in degree mode so let me try again

36. anonymous

yayy i got 209.69

37. anonymous

Good....close enough to 210. :)

38. anonymous

next problem b=58.2 c=68.3 C=51.3 degrees were gunna find a

39. anonymous

At this point, it is simply plugging in values into that sine rule ratios and cranking out numbers in a calculator. There is not much help you need.

40. anonymous

yeaa but i want to do it my self then have someone do it so i can nn check my answer to make sure its correct

41. anonymous

i got 7105. 88

42. anonymous

is my answer correct thats all im asking

43. anonymous

It can't be that big.

44. anonymous

Angles are almost close to each other. So, side lengths have to be close to each other too.

45. anonymous

well i must be doing something wrong but sin68.3/51.3=.018111746

46. anonymous

128.7/.018111746=7105.88

47. anonymous

b=58.2 c=68.3 C=51.3 degrees SinB/b = SinC/c => SinB = 58.2 * Sin(51.3)/68.3 => SinB = 0.665 B = 41.68

48. anonymous

becuase i couldnt find A or B so i figured they were the same by suntracting 180-51.3

49. anonymous

ohhh ok so u must follow the formula

50. anonymous

Now that you know B, you find A by doing 180 - 51.3 - 41.68 = 87

51. anonymous

noww i get it

52. anonymous

SinA/a = SinC/c => a = c * SinA/SinC => a = 68.3 * Sin(87)/Sin(51.3) => a = 87.4

53. anonymous

ok

54. anonymous

@dessyk The following variations of Law of Sines are the same: $\frac{a}{\sin(A)} = \frac{b}{\sin(B)}=\frac{c}{\sin(C)}$ and $\frac{\sin(A)}{a}=\frac{\sin(B)}{b}=\frac{\sin(C)}{c}$

55. anonymous

He got that. :)

56. anonymous

ok :)

57. anonymous

hello

58. anonymous

yeah

59. anonymous

i have another question but hoew did you get 41. sometrhing but i got 45.42

60. anonymous

You mean for B = 41? I did the inverse sine function on the value 0.665.

61. anonymous

yes, ohh reallyy you see im confused now i thought u just i thought u just took .6650*68.3=45.42

62. anonymous

Sin(B) = 0.665 => B = inverse sine (0.665). On the calculator, you have to first press 0.665. Then, inv button, then the sin button.

63. anonymous

That gives you angle B.

64. anonymous

i didnt get that

65. anonymous

dessyk.. nice drawing.. :) :)

66. anonymous

thank you i guesss lol can yoiu help me!!

67. anonymous

what is the question

68. anonymous

its up above next problem b=58.2 c=68.3 C=51.3 degrees were gunna find a

69. anonymous

law of sines

70. anonymous

i didn't see above but u can find it very easily.. the formula is sin a / a = sin b / b = sin c / c or a /sin a = b / sin b = c / sin c use any of them what caters ur problem

71. anonymous

okay but when i tried i started to get fustrated because i wasnt getting the righ tanswer

72. anonymous

did my answer help u even a bit or not ?

73. anonymous

a little bit its just that i need help going through the process

74. anonymous

|dw:1335070736451:dw|

75. anonymous

|dw:1335070848159:dw|

76. anonymous

get it?

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