cross ratio
- a ratio relating four points in the real or complex plane.
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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
Historical Examples
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.