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Math Help - Parabolas: Given the Directrix and Vertex. Find "P"

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    Parabolas: Given the Directrix and Vertex. Find "P"

    Vertex: (1,1)

    Directrix: Y = 9/8

    please help me find "P"
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  3. #3
    Super Member bigwave's Avatar
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    Cool

    Quote Originally Posted by AirSaints View Post
    Vertex: (1,1)

    Directrix: Y = 9/8

    please help me find "P"
    recall that "P" is a collection of points on the parabola such that

     <br />
d(F,P)=d(P.D)<br /> <br />

    so in this case since we only know where the Vertex is and Diretrix
    we can only give the value of one point of P which is the vertex itself

    the distance from the vertex to the directrix is 1/8 and the distance from the vertex to the focus is 1/8
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    recall that "P" is a collection of points on the parabola such that
    d(FP)= d(DP)
    Uh, bigwave, using that definition, "P" is the parabola itself. The wikipedia article Wilmer links to uses "P" mean the distance from the vertex to the focus which, as Wilmer points out, is the same as the distance from the vertex to the diretrix, 1/8. P= 1/8.
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