Coxeter- Figure 7.4A

The polar of a point [math]X[/math] in the polarity [math](ABC)(Pp)[/math] is the line [math]X_1X_2[/math] determined by: [math]A_1 = a\cdot PX, P_1 = p\cdot AX, X_1 = AP\cdot A_1P_1,[/math] [math]B_2 = b\cdot PX, P_2 = p\cdot BX, X_2 = BP \cdot B_2P_2[/math].