The product formula of vector a and vector b is: ab = x1x 2+y1y2 = | a ||| b | cos θ.

The analysis is as follows:

The vector a=(x 1, y 1) and the vector b=(x2, y2).

Ab = x1x 2+y1y2 = | a || b | cos θ (θ is the angle between a and b).

Vector is not called "product", it is called quantity product. For example, A and B are called the quantitative product of A and B or the point A multiplied by B. ..

Binary product:

Given three vectors A, B and C in a space, if the two vectors A and B are cross-product a×b first, then the obtained vector and the third vector are cross-product, then the final result is still a vector.

Nature:

(a×b)×c=(a c) b-(b c) a

a×(b×c)=-(b×c)×a=(a c) b-(a b) c