Let us take a problem in 3D?
Consider the triangle A(0,0,0), B(1,1,1) and C(0,0,1). What is the area of this triangle?
Solution:
As we cannot plot these points, we analyse them as where they lie in 3D. A lies at origin, B is equidistant from all planes of the first octant. C is on Z axis. This triangle is right angled with base =1, height=1. Therefore area is 1/2 × base×height.Answer. 0.5 sq.units.