Senior high school mathematics vector compulsory four. Compulsory four is to learn the definition of trigonometric function first, then plane vector, and then trigonometric transformation. Plane vector is a quantity with both direction and magnitude in two-dimensional plane, which is also called vector in physics.

Vector, also known as Euclidean vector, geometric vector and vector, refers to quantities with magnitude and direction. It can be imagined as a line segment with an arrow. The arrow represents the direction of the vector, and the length of the line segment represents the size of the vector. The quantity corresponding to a vector is called a quantity (called a scalar in physics), and a quantity (or scalar) has only a size and no direction.