Biangular coordinates

In mathematics, biangular coordinates are a coordinate system for the plane where $C_1\,\!$ and $C_2\,\!$ are two fixed points, and the position of a point P not on the line $\overline{C_1C_2}\,\!$ is determined by the angles $\angle PC_1C_2\,\!$ and $\angle PC_2C_1\,\!$ .

References

G. B. M. Zerr Biangular Coordinates, American Mathematical Monthly 17 (2), February 1910
Naylor, “A New Kind of Geometry: the Biangular Coordinate System”
J. C. L. Fish.Coordinates Of Elementary Surveying, p.38, READ BOOKS, 2007
George Shoobridge Carr. Formulas and theorems in pure mathematics. p.742. Chelsea Pub. Co., 1970
Howard W. Baeumler. Biangular coordinates. University of Buffalo, 1950