For example:
pts = {{0, 1}, {-(Sqrt[3]/2), -(1/2)}, {Sqrt[3]/2, -(1/2)}};
trig=JoinedCurve[Line[pts], CurveClosed -> True];
Then trig is a closed triangle. If I have a point p={a,b}, how can I judge if p is in the interior of the triangle trig?