The beauty of programming---whether the point is within a triangle

Three vertex coordinates of a known triangle, judging whether a point is in a triangle (we also see it as a triangle on the side of the triangle)

Solution one: By connecting the points and three vertices to calculate the area of the triangle of each edge of the point and triangle, and then compare the three areas together with the original triangular area.

Solution two: Starting from the relationship between the point and the line, if the point in the triangle, then along the border of the triangle counterclockwise, point must remain on the left side of the boundary, can be determined by the two vector cross product of positive or negative to determine whether on the left.

The beauty of programming---whether the point is within a triangle