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Homework Help: Compositions Of 2 Relations, one is the Entire Plane

  1. Mar 30, 2012 #1
    1. The problem statement, all variables and given/known data
    Sketch the compositions

    S of R

    R of S

    2. Relevant equations
    The relations to be... "composition'ed?".
    R= R^2, the XY plane, i.e. {(x,y)}, the set pf all (x,y)

    S= {(x,y) : y=x^3}, set of all (x,y) such that y=x^3

    For example

    R of S = {(a,c) : [itex]\exists[/itex]b such that a^3=b and {(b,c)}}

    3. The attempt at a solution
    I feel it should end up being all of R^2, but this seems too simple. For R of S, S maps a into[itex]\sqrt[3]{b}[/itex], then R maps b into, c. But that c is all real numbers. I have done these before, and the teacher wants a graph of a as x, and c as y. Because c will be all real for each b, this will be a succession of vertical lines. But I can see no restrictions on a to prevent the final graph from just being all of the plane (the ac place now).
  2. jcsd
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