Learning Summary- ry. Vector Cross Product

Learning Summary- ry. Vector Cross Product

Assume there are vectors P (x1, y1) and Q (x2, y2)
The cross product of vector P and Q is expressed as P × Q.
And P × Q = x1? Y2? X2? Y1

Properties of cross product:
A very important feature is to use its symbols to determine the clockwise relationship between the two vectors:
If P × Q> 0, P is clockwise in Q;
If P × Q <0, P is in the counterclockwise direction of Q;
If P × Q = 0, P and Q are in the same line, but they may be reversed in the same direction.

· Clockwise

· Counterclockwise

Apply, give a sequence of points, and determine whether it is clockwise or counterclockwise: Calculate the cross product of two consecutive points, including the first and last, find their sum, greater than 0 is clockwise, if the value is less than 0, it is counter-clockwise.