The normal vector of the cross product method is that the cross product represents the area of the parallelogram, while Pingsi has a direction, and the direction is the normal vector. The normal vector of a plane is perpendicular to the plane. The vector product of parallel vectors is equal to zero. The vector product of two nonparallel vectors in a plane perpendicular to the plane is the normal vector.

The origin of vectors

Vector can enter mathematics and develop, first of all, we must talk about the geometric representation of complex numbers. /kloc-At the end of 0/8th century, Norwegian surveyor wiesel first expressed complex numbers with points on the coordinate plane, and defined vector operations with geometric complex operations. Points on the coordinate plane are represented by vectors, and the geometric representation of vectors is used to study geometric problems and trigonometric problems.

People gradually accepted the complex number, and learned to use it to represent and study the vector on the plane, so the vector quietly entered mathematics.