Plane vector is a quantity with both direction and magnitude in two-dimensional plane, which is also called vector in physics, as opposed to a quantity with only magnitude and no direction. Plane vectors are represented by small arrows above A, B and C, and can also be represented by the first and last letters of vector directed line segments.
Vector projection:
Projection means that the shadow of a figure is projected on a surface or a line. Projection is the shadow of an object on the ground under the sunlight. When sunlight is perpendicular to the ground, it is orthogonal projection, which is the projection studied in linear algebra. When the object is perpendicular to the ground, the shadow length is 0.
Let the included angle between two non-zero vectors A and B be θ, then | b | cos θ is called the projection or nominal projection of vector B in the direction of vector A, and the projection of one vector in the direction of another vector is a quantity, which is called the projection vector.
Cross product, also known as outer product, cross product, vector product and cross product, is a binary operation of vectors in vector space. Its operation result is a vector instead of a scalar, and the cross product of the two vectors is perpendicular to the sum of the two vectors. It is usually used in physical optics and computer graphics.