contrafocaladj.
/kɒntrəˈfəʊkəl/ Mathematics.
Having, as two conics or conicoids, the sums of the squares of two corresponding axes equal: opposed to confocal adj. and n. conics, etc. in which the differences are equal.
ΚΠ
1866 J. J. Sylvester in Philos. Trans. (Royal Soc.) 156 760 Contrafocal ellipsoids, the sums of whose squared axes are the same in all three directions.
1868 E. J. Routh Rigid Dynamics 358 The momental ellipsoids of these bodies are contrafocal, i.e. have the sum of the squares of any two principal diameters the same in each ellipsoid.
Derivatives
contrafocalism n. the property of being contrafocal.
ΚΠ
1866 J. J. Sylvester in Philos. Trans. (Royal Soc.) 156 771 For the two cases of con- and contra-focalism it will be convenient to disregard this uniform motion of rotaion.
This entry has not yet been fully updated (first published 1893; most recently modified version published online June 2018).
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adj.1866