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Find angle of a triangle with given sides

  1. Apr 26, 2005 #1
    In a triangle ABC, AB=7, BC=8, CA=9, find angle B correct to 3 significant figures.
    The answer is 73.4, but i don't know how to calculate it, thanks.
     
  2. jcsd
  3. Apr 26, 2005 #2

    arildno

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    Use the cosine rule.
     
  4. Apr 26, 2005 #3

    dextercioby

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    U'll need a calculator to compute B,i.e.solve the equation

    [tex] \cos B=value[/tex]

    and select the first 3 decimals the calculator shows u...

    Daniel.
     
  5. Apr 26, 2005 #4
    O, I forgot there is a rule called " cosine rule" in the world, thanks.
     
  6. Apr 26, 2005 #5

    arildno

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    The world hath many rules, none of which you ought to ignore..:wink:
     
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