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Thread: [SOLVED] trignometery law of cosines

  1. #1
    ramisha
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    [SOLVED] trignometery law of cosines

    in triangle , p=5 cm, q=7cm and angle R=60 degrees. find r.
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  2. #2
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    Hello, ramisha!

    In triangle: $\displaystyle p=5$ cm, $\displaystyle q=7$ cm and $\displaystyle \angle R=60^o$ . Find $\displaystyle r.$

    This is a straight-forward application of the Law of Cosines: .$\displaystyle r^2\;=\;p^2 + q^2 - 2pq\cos R$

    We have: .$\displaystyle r^2 \:=\:5^2 + 7^2 - 2(5)(7)\cos60^o$

    Can you finish it?

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