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Math Help - using sine and cosine

  1. #1
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    Exclamation using sine and cosine

    A scalene Triangle With a Side A 12m Long Side B 5m long and one angle which is opposite length A at 2.1 rad

    help with knowing the rest of the angles in degrees and also the other side please
    Last edited by scholezy93; February 5th 2013 at 12:06 PM.
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  2. #2
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    Re: using sine and cosine

    Use the sine rule to find angle B.

    Use the fact that the angles add to 180 degrees to find angle C.

    Use the sine rule to find side c.
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    Re: using sine and cosine

    Or you could use the cosine law: a^2= b^2+ c^2- 2bc cos(A) with a= 12, b= 5, and A= 2.1 to get a quadratic equation to solve for c. Note that there may be two different values for c and so two different triangles.
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