Represents the AF vector, BC vector and FB vector, and then sets the normal vector n(x, y, z) of the plane FBC. Because n is perpendicular to the plane FBC, the normal vector n * BC.
Normal vector n*FB vector =0, find the normal vector n, if the vector AF =λ times the normal vector n (that is, the * * * line between them), then it can be said that AF is perpendicular to the plane FBC. It can be directly proved that AF is perpendicular to FB and AF is perpendicular to BC, that is, AF is perpendicular to the plane FBC.
Geometric representation
A vector can be represented by a directed line segment. The length of the directed line segment indicates the size of the vector, the size of the vector, that is, the length of the vector. A vector of length 0 is called a zero vector, and a vector of length 1 unit is called a unit vector. The direction indicated by the arrow indicates the direction of the vector.