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Posted by on Thursday, April 5, 2012 at 11:43pm.

Find the indicated angle è. (Use either the Law of Sines or the Law of Cosines, as appropriate. Assume a = 95 and c = 137(angle B=38). Round your answer to two decimal places.)

  • Trig Help Please!!! - , Friday, April 6, 2012 at 12:44am

    Your given information is of the format SAS , so it requires the cosine law to find c

    c^2 = 95^2 + 137^2 - 2(95)(137)cos 38°
    c = 85.335

    I would now find angle A using the sine law, then the third angle is easy.

  • Trig Help Please!!! - , Friday, April 6, 2012 at 1:21am

    i got that far too but i cant figure out the angle C!!!!

  • Trig Help Please!!! - , Friday, April 6, 2012 at 9:17am

    Just noticed that I was actually finding b, not c
    (c was given)
    No harm done here.

    let's find angle A by the sine law

    sinA/a = sinB/b
    sinA/95 = sin 38/85.335
    sinA = .685...
    A = 43.27

    then angle C = 180-38-43.27 = 97.73° or appr 98°

    The problem with the sine law is that we run into the "ambiguous case".
    since the sine is positive in I and in II, when we take the inverse sine, we often cannot tell which angle to use.
    In this case, since the largest angle is always opposite the largest side, angle C must be the largest.
    So I try to avoid finding that angle by the sine law, and I found angle A instead.
    Since any triangle could have only ONE obtuse angle, by finding one of the two smaller angles we avoid that problem

  • Trig Help Please!!! - , Friday, April 6, 2012 at 12:12pm

    thank you!!!

  • Trig Help Please!!! - , Saturday, May 26, 2012 at 2:50pm


  • Trig - , Saturday, May 26, 2012 at 2:52pm

    i dot geht thhis werlk? cahn sumwone elp meh?

  • Trig Help Please!!! - , Tuesday, July 24, 2012 at 1:41am

    I didn't know this, and I feel like I was cheated by my geomtery teacher.I feel like I should have known this I am a math professor with a Ph.D. but I'm comforted to hear that a lot of other people didn't know about it, either.

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