How can I display graph with oxyplot ?

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C#

graphics

chart

graph

I want to display a graph for an ellipse whose parameters are x and y, so i need the fonction oxyplot to have instruction like this :

What I have tried:

x = (x1+x2)/2 + X*Math.Cos(w) - Y*Math.Sin(w);
y = (y1+y2)/2 + X*Math.Sin(w) + Y*Math.Cos(w);
plot(x,y);