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Math Help - Triangle length question.

  1. #1
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    Triangle length question.

    Hey, I am stuck on a question and I'd really appreciate an answer with some explaining on how to use it. It would be greatly appreciated. Also, I apologise if there is similar question to this.

    "A triangle has two sides of 25cm and 30cm. The angle between the two sides is 30 degrees."
    I have found the area, which is: 187.5cm2

    I just need to find the other length, which is where I am having difficulty.
    Thanks ^____^
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  2. #2
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    How did you find the area?
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  3. #3
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    In Triangle \angle ABC

    Area = \frac{1}{2}\times a\times b\times \sin(C)

    Therefore the poster found the area as follows

    Area = \frac{1}{2}\times 25\times 30 \sin(30 ) \approx 187.4

    To find the other length use the Cosine rule with the values you used to find the area

    a = 25
    b= 30
    C = 30

    Cosine rule is

     <br />
c = \sqrt{a^2+b^2-2ab\times \cos(C)}<br />

    Spoiler:
    c \approx 15
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