## Mimi_x3 Group Title Amy is 20m S30°W from a tree. Belinda is 50m 110° T from the same tree. Find the distance between them, to the nearest metre. 2 years ago 2 years ago

1. fiddlearound Group Title

what do S30°W and 110° T mean ?

2. Mimi_x3 Group Title

Um, I'm not sure but i think South 30 degrees West , 110 degrees true bearing idk. I haven't done it in ages so I forgot xD

3. fiddlearound Group Title

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4. fiddlearound Group Title

like that ^^^ ?

5. fiddlearound Group Title

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6. Mimi_x3 Group Title

Um, idk , it looks right though xDD

7. Mimi_x3 Group Title

How can I find the distance between them ?

8. fiddlearound Group Title

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9. Mimi_x3 Group Title

Um, I don't think that it requires sin and cos, its bearings

10. fiddlearound Group Title

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11. Mimi_x3 Group Title

What? There's not values of x and y, how can you use the distance formula ?

12. fiddlearound Group Title

I got the values of x and y using the sin() and cos() in the table I drew above. Rounded to the nearest metre, I get 64 meters distance.

13. Mimi_x3 Group Title

Okay, tyvm (:

14. fiddlearound Group Title

does it make sense ? did you learn this stuff in the past ?

15. Mimi_x3 Group Title

Not in the past xD, I learnt it year 7 and now I forgot xD But I remember that there's an easier way that doesn't require sin and cos

16. fiddlearound Group Title

Well , if there is an easier way, I hope someone will post it here - coz I'd like to know it too :)

17. Mimi_x3 Group Title

Hey, you know your diagram what is the angle degrees thing for AB

18. fiddlearound Group Title

what do you mean ?

19. Mimi_x3 Group Title

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20. fiddlearound Group Title

yes we can calculate that - it's 240-110 = 130 degrees

21. fiddlearound Group Title

and you're right that we can make the problem simpler

22. Mimi_x3 Group Title

Yep, there's a formula to calculate it then, was it the sine or cosine formula ? or was it soh cah toa ?

23. fiddlearound Group Title

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24. Mimi_x3 Group Title

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25. fiddlearound Group Title

I would need to calculate to find out - why are you asking ?

26. Mimi_x3 Group Title

If that angle can be found, then I can use the sine rule xD

27. fiddlearound Group Title

are you trying to use the law of the cosines ?

28. Mimi_x3 Group Title

No, the Sine Rule it says it in my book xD

29. fiddlearound Group Title

which sine rule ? a/sin(A)=b/sin(B)=c/sin(C) ?

30. upsilon Group Title

Yes, that's it @fiddle

31. Mimi_x3 Group Title

Yep that xD

32. fiddlearound Group Title

yes, but we only have one angle , that 130 degrees at this point.

33. Mimi_x3 Group Title

I know , but the other angle is 30 right ? the one that I drew

34. fiddlearound Group Title

why did you pick 30 degrees ?

35. fiddlearound Group Title

is it becasue sin(30)=1/2 ?

36. Mimi_x3 Group Title

Well, the question S30°W so that angle is 30 right ?

37. fiddlearound Group Title

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38. upsilon Group Title

No, you can't say that...@mimi|dw:1315634688202:dw|

39. fiddlearound Group Title

The 30 degrees would be relative to the black line I drew.

40. fiddlearound Group Title

yeah, upsilon says the same thing.

41. Mimi_x3 Group Title

Can it be 60 then, since 90-30 = 60 ?

42. upsilon Group Title

You can't decide like that you need the angle to be in ratio with the opposite sides...

43. fiddlearound Group Title

yep

44. fiddlearound Group Title

but the law of the cosines might work here.

45. fiddlearound Group Title
46. upsilon Group Title

Yea, that will work

47. fiddlearound Group Title

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48. upsilon Group Title

$d = \sqrt{ a^2 + b^2 - 2*a*b*cos\alpha}$

49. Mimi_x3 Group Title

Okay, tyvm (:

50. fiddlearound Group Title

http://www.wolframalpha.com/input/?i=sqrt%2820^2%2B50^2-2*20*50*cos%28130%29%29 It's 64 , same answer I got with the first method :)

51. Mimi_x3 Group Title

Ok, ty (:

52. fiddlearound Group Title

and it's much shorter than the first method :)

53. Mimi_x3 Group Title

yup xD. Your method looked so complicated before (: