Introduction
Three dimensional plane of Class 11
THE PLANE
A plane is a surface such that if any two points are taken on it, the line segment joining them lies completely on the surface. In other words, every point on the line segment joining any two points lies on the plane.
The general equation of a plane is ax + by + cz + d = 0. There are only three
unknowns, because the equations ax + by + cz + d = 0 can be written as 
= 0 or Ax + By + Cz + 1 = 0. Thus, to find a plane we must have three conditions to find the values of A, B and C.
