Determines if a point c is left of the line defined by the points a and b. This is equivalent to determining whether the points a, b, and c are in counter-clockwise (CCW) order. @param xa x coordinate of point a. @param ya y coordinate of point a. @param xb x coordinate of point b. @param yb y coord
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double xa, double ya,
double xb, double yb,
double xc, double yc)
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