1. POINTS IN 3 DIMENSIONS 2D The xy-plane is used to plot points in 2D.
We look down on this from above.

2. 3D NB: Z X-axis left to right. Y Y-axis front to back.
Z-axis top to bottom. X
NB:
(a) All 3 axes are perpendicular to each other.
(b)(i) X-axis is perpendicular to yz-plane.
(ii) Y-axis is perpendicular to xz-plane.
(iii) Z-axis is perpendicular to xy-plane.

3. Ex
Suppose we have a cuboid measuring 4 X 3 X 6 fitted against the axes as shown. Z
O is (0,0,0) Y D E
A is (4,0,0) F
B is (4,3,0) G
C is (0,3,0)
D is (0,3,6) 6
E is (4,3,6) C B
F is (4,0,6) 3 X O 4 A
G is (0,0,6)
( ) - ( )
= ( )
( ) 4 4 4
GB = b – g = 3 3
GB = 3 6 -6 -6
By inspection
Using rule from 2D.

4. NB: On X-axis y = 0 and z = 0. Points O & A.
On Y-axis x = 0 and z = 0. Points O & C.
On Z-axis x = 0 and y = 0. Points O & G.
In xy-plane z = 0. Points O, A, B & C.
In xz-plane y = 0. Points O, A, F & G.
In yz-plane x = 0. Points O, C, D & G.