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Re: Interesting Math Error

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  • Geezer
    I think I found the answer, Pete. http://imgs.xkcd.com/xk3d//(_frame.png Larry
    Message 1 of 25 , Apr 1 12:14 AM
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      I think I found the answer, Pete.

      http://imgs.xkcd.com/xk3d//(_frame.png

      Larry


      --- In SeattleRobotics@yahoogroups.com, "Pete Miles" <robots@...> wrote:
      >
      > x^n and -x^n and (-x)^n are considered unary operations
      >
      > (x-y)^n, -(x-y)^n, and (sin(theta)-cos(theta))^n are not unary operatations
      >
      > This is the root of the Math Error:
      > Forcing -(x-y)^n TO BE EQUAL to (-x+y)^n
      >
      > These two relationships are NOT equal
      >
      > The systems that are calculating this incorrectly, are incorrectly passing the -
      > sign inside all operators inside the parentheses when the contents of the
      > parentheses are raised to a power.
      >
      > There are 2 schools of thought here:
      > -(3-5)^2 = will equal either -4 or +4 Only one answer is correct
      >
      > Now what would the following answer be to this relationship?
      > 0-(3-5)^2
      > is it -4 ??
      > or is it +4 ??
      >
      > -(3-5)^2 IS EQUAL to 0-(3-5)^2
      >
      > Yet most of the the systems that incorrectly calculate -(3-5)^2
      > will correctly calculate 0-(3-5)^2
      >
      > For you trig people:
      > if sin(30) = 0.5 then -sin(30) = -0.5
      >
      > Now (sin(30))^2 + (cos(30))^2 = 1
      >
      > Solving for sin(30)
      > (sin(30))^2 = 1-(cos(30))^2
      >
      > sin(30) = +(1-(cos(30))^2)^0.5 or -(1-(cos(30))^2)^0.5
      >
      > if you believe that -(5-3)^2 = +2
      >
      > then you must believe that
      >
      > sin(30) = +0.5 or i/2
      >
      > This math error has far reaching implications
      >
      > Pete
      >
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