- a ratio relating four points in the real or complex plane.
Origin of cross ratio
First recorded in 1880–85
Also called anharmonic ratio.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
Examples from the Web for cross ratio
The cross-ratio of four points equals that of the four conjugate points.
Before we draw conclusions from this result, we must investigate the meaning of a cross-ratio somewhat more fully.
If we take the points in a different order, the value of the cross-ratio will change.
It is convenient to let the point at infinity occupy the last place in the symbolic expression for the cross-ratio.
The cross-ratio of any four points in one equals that of the corresponding points in the other.