Solve for cos A

Discussion in 'Other Pre-University Math' started by nycmathguy, Jul 10, 2022.

  1. nycmathguy

    nycmathguy

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    IMG_20220710_085222.jpg
     
    nycmathguy, Jul 10, 2022
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  2. nycmathguy

    MathLover1

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    last line is incorrect

    a^2-b^2-c^2= (-2bc)*cos(A)
    (a^2-b^2-c^2)/(-2bc) = cos(A)
    -(a^2-b^2-c^2)/(2bc) = cos(A)
    (-a^2+b^2+c^2)/(2bc) = cos(A)
     
    MathLover1, Jul 10, 2022
    #2
    nycmathguy likes this.
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  3. nycmathguy

    nycmathguy

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    I tried. I did my best. Can't get them all right.
     
    nycmathguy, Jul 11, 2022
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