If Q, P be the points of contact of the common tangent, and A, a the points in which the tangent is cut by the third conic, then, by Art. 206, P, Q are the foci of an involution of which A and a are conjugate points. .ac. by Art. 201, QAPa is harmonic.
|Title||:||Solutions of examples and problems in conic sections|
|Author||:||William Henry Besant|