Often it is necessary to use, in addition to the distance and the quota, the x-axis.

The plan of reference for the x-axis is the lateral projection plane or πo. 

To the left of this plane, the x-axis has positive values, to the right, they have negative values. 

In the projections, it is the≡z line that serves as a reference for marking the x-axis.

When the three coordinates of a point are given, this does not mean that you have to represent
the three projections. 

The x-axis value serves to locate the point along the x-axis, to the left or the right of y≡z, or a reference point marked on the x-axis.