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Find angle of a triangle with given sides

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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.
 

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arildno
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Use the cosine rule.
 
  • #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.
 
  • #4
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O, I forgot there is a rule called " cosine rule" in the world, thanks.
 
  • #5
arildno
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The world hath many rules, none of which you ought to ignore..:wink:
 

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