Calculate the length of a side of a triangle knowing

Discussion in 'Geometry and Trigonometry' started by MathNoob, Oct 26, 2021.

  1. MathNoob

    MathNoob

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    Knowing the length of one side of a triangle and the ratio between the other two sides and the angle between the side I know the length of and one of the other sides, how do I calculate the length of that side? mathhelp.PNG
     
    MathNoob, Oct 26, 2021
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  2. MathNoob

    MathLover1

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    use cosine law:
    [​IMG]
     
    MathLover1, Oct 26, 2021
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  3. MathNoob

    MathNoob

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    Shouldnt it be the angle between a and b instead of alpha in the expression?
     
    MathNoob, Oct 26, 2021
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  4. MathNoob

    MathLover1

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    in this case yes
    upload_2021-10-26_13-11-56.jpeg
    in your drawing the angle would be between c and b

    since given the ratio between the other two sides, use the ratio a/c

    are you given any values for b, a/c, and alpha?

    if you know the ratio, whatever fraction it is, numerator is equal to length of side a and denominator is equal to length of side c
     
    MathLover1, Oct 26, 2021
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  5. MathNoob

    MathNoob

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    I thought the sizes are somehow relative to the angle.
    The ratio could be 1/2 or 2/4...
     
    MathNoob, Oct 26, 2021
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  6. MathNoob

    MathLover1

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    if a/c=1/ 2 then c=2a or a=c/2 ; then in formula above, you express a as c/2

    whatever the ratio is, use it to express side a in terms of side c
     
    Last edited: Oct 26, 2021
    MathLover1, Oct 26, 2021
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  7. MathNoob

    nycmathguy

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    I'm back. I couldn't stay away from math for too long.
     
    nycmathguy, Oct 27, 2021
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