Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. In Euclidean geometry, every triangle has two isodynamic points, usually denoted as S and S''. These points are the common intersection points of the three circles of Apollonius associated with the triangle; hence, the line through these points is the common radical axis for these circles. The centers of these circles are collinear; they all fall on the Lemoine line, which is perpendicular to the radical axis defined by the isodynamic points.