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Math Help - Rearranging an equation with a cosine

  1. #1
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    Rearranging an equation with a cosine

    I have an equation that calculates the distance between two coordinates on Earth. The problem is, I need to rewrite this equation to solve for a different variable.

    D=Distance in feet
    X=Person's longitude
    Y=Person's latitude
    A=Some place's longitude
    B=Some place's latitude

    D=5280*(SQRT( (69.1*(B-Y))^2 + (69.1*(A-X)*COS(Y/57.3)) ))

    How can I rearrange this equation to solve for A not D?

    Thanks
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  2. #2
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    First 2 steps are.

    Divide both sides by 5280.

    After that, square both sides.

    Now show me some work..

    I will then help some more.
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  3. #3
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    I'll raise you the next three steps (subtracting, dividing, then adding) if you check my work!

    A = ( (((D/5280)^2)-((69.1*(B-Y))^2)) / 69.1*COS(Y/57.3) ) + X

    I was really intimidated with this because of the giant square root sign, and the COS which I haven't used before. But once I did the first two steps, it just unraveled for me. I hope I did it right.
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  4. #4
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    I agree with your answer.
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  5. #5
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    Thank you very much!
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