# Plotting a dot product [closed]

From a conic equation obtained from a dot product, I want to plot its 2D graph, while being able to manipulate the variable.

Manipulate[
K = {Sin[t] Cos[p], Sin[t] Sin[p], Cos[t]};
oP = {x, y, 1};
noP = Assuming[Element[{x, y, z}, Reals], Simplify[Norm[oP]]];
nK = Assuming[Element[{t, p, x, y, z}, Reals], Simplify[Norm[K]]];
{(K.oP)^2 == (Cos[a]*nK*noP)^2},
{a, Pi/16, Pi, Pi/16, ControlPlacement -> Left},
{t, 0, \[Pi], \[Pi]/256, ControlPlacement -> Left},
{p, 0, \[Pi], \[Pi]/256, ControlPlacement -> Left}
]


I do get the correct equation, but I am unable to plot it in any way when I take it separatly.

ParametricPlot[ 1 == (1 + x^2 + y^2) Cos[\[Pi]/16]^2, {x, -14, 14}, {y, -14, 14}]


show the axes, but not the graph.

Only when I try with the == function do I get the graph, which is not really useful... What should I change?

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Seems to belong to mathematica.stackexchange.com –  martini Nov 3 '12 at 22:24
This is not off topic, as per the FAQ, listed under "Software that mathematicians use". That being said, it has now been asked here (so you can expect this to be closed as "off topic"). –  Douglas S. Stones Nov 3 '12 at 23:06
This has been asked and answered on Mathematica.SE. Closing this instance. –  robjohn Nov 3 '12 at 23:20