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Help with conic transformations

Discussion in 'Mathematics' started by mostlymaths, Sep 19, 2018.

  1. mostlymaths

    mostlymaths New commenter

    Hello - helping someone here can help my stupid brain.
    I was looking at rotations for the first time today and the new spec text book just gives the rules. I decided to look at some graphs to see if I could show the students, when introducing the idea, how these rules were formed. So for a parabola in form of y^2 = kx, if we rotate by 90 degrees clockwise the coordinate rule is that (x,y) becomes (y, -x). However the book says that when transforming the equation x is replaced by -y and y by x. I graphed some examples on Autograph and this rule is correct. Now I'm aware that I'm probably missing something really simple but can someone explain the link between the coordinate rule and the rule for transforming the equation. For once google has proved fruitless :-(
  2. Vince_Ulam

    Vince_Ulam Star commenter

    By convention, rotations of axes are anticlockwise. That particular coordinate rule is just a quick & dirty way of finding the address of a point following a -270° rotation, performing no actual rotation itself.
  3. MathsMum5

    MathsMum5 New commenter

    Okay - thanks - so I'm looking for a connection that is not there!

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