cosine rules

Discussion in 'Math' started by amilton542, Jan 30, 2011.

  1. amilton542

    Thread Starter Active Member

    Nov 13, 2010
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    ive been working on sine and cosine rules out this book, but they only do one example of each so ive had to rearrange them for the complete set but i still end up with the same angle using either, just need some clarification wether there right:

    for e.g a/SIN A = b/SIN B = c/SIN C ,

    a = c x SIN A/SIN C. SIN A = a x SIN B/B

    b = a x SIN B/SIN A. SIN B = b x SIN C/C

    c = b x SIN C/SIN B. SIN C = c x SIN A/A
     
    Last edited: Jan 30, 2011
  2. Georacer

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    Can you include parenthesis and keep the notation constant to be more specific?
    They seem right but I can't be sure if you alternate the letter for the sides from small to capital.
     
  3. amilton542

    Thread Starter Active Member

    Nov 13, 2010
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    TWO ANGLES given plus ANY SIDE
    a = b x SIN A / SIN B
    b = c x SIN B / SIN C
    c = b x SIN C / SIN B

    TWO SIDES given plus an ANGLE NOT ENCLOSED by them
    SIN A = a x SIN B / b
    SIN B = b x SIN C / c

    ive created numerous triangles and i think this is write so far but for SIN C theres two where the answer is very close for each and i dont no what ones write:
    SIN C = c x SIN B / b (i believe this may be the correct one)
    SIN C = c x SIN A / a
     
  4. studiot

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  5. Georacer

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    All of your formulas are correct, but be careful when trying to find an angle, as Papabravo stated. You will get 2 answers and you must use your intuition and problem data to filter the wrong one.

    The video linked is very informative.
     
  6. studiot

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    Have I been promoted?
     
  7. Georacer

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    I don't know about you, but E-book Developer is the highest rank I 'd like to have. Any higher and it would be too much work on the site to keep me interested in.
     
  8. studiot

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    It's not all milk and honey you know.
    Especially since they won't adopt my suggestion of free beer for this rank.

    No, by promotion I was thinking of being compared to papabravo and his ghost presence in this thread.
     
  9. Georacer

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    Free beer, eh? I 'm not in heaven yet, so I guess I can't have any.

    As for your rep, I can't verify it personally, only time can.
    Especially if you consider the phrase that says "Only after someone's death you can judge him properly", or something like that.

    I for once, don't want to compete for the position of the "Math guru". What I would like however is the visitor of the site to acknowledge the time I spend here and that I generally provide correct answers.
     
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