Home page  Catalogue  Classes  Tables  Glossary  Notations  Links  Bibliography  Thanks  Downloads  Related Curves 

X(1), X(2), X(3), X(4), X(6), X(9), X(57), X(223), X(282), X(1073), X(1249), X(3341), X(3342), X(3343), X(3344), X(3349), X(3350), X(3351), X(3352), X(3356) excenters Ia, Ib, Ic and more generally the extraversions of all the weak points such as X(9), X(57), etc midpoints of ABC, midpoints of altitudes E(1986), E(1987) : real foci of the inscribed Steiner ellipse Q1, Q2, Q3 vertices of the Thomson triangle other points below 

The Thomson cubic is the isogonal pK with pivot the centroid G = X(2). See Table 27. It is sometimes called 17point cubic in older literature. It is the complement of the Lucas cubic. See Table 21 for cubics anharmonically equivalent to the Thomson cubic. The isotomic transform of K002 is K184. K002 is a member of the class CL043 : it meets the circumcircle at A, B, C and three other points Q1, Q2, Q3 lying on several rectangular hyperbolas (see below). The tangents at these points are concurrent at a point X on the lines X(2)X(1350) and X(64)X(631). See K346 and also Q063. Locus properties :


Points on the Thomson cubic 

The following table gives the repartition of points on K002 : for any P on K002, the points P*, Q= G/P, R, T are its isogonal conjugate, GCeva conjugate, Kcrossconjugate, tangential respectively and all these points lie on K002. Recall that the triples P, P*, X(2)  P, Q, X(6)  P, R, X(3)  Q, G/P*, X(4) are collinear on K002. Construction of T : let N be the harmonic conjugate of G with respect to P and P* and let N* be its isogonal conjugate. The tangents at P and P* pass through N*. T also lies on the line passing through G/P* and (G/P)*. The green points are weak points hence their extraversions lie on K002. 



E(1986) and E(1987) are the real foci of the Steiner inscribed ellipse. When a point is not in ETC, a SEARCH number is given. 

K002 contains :
These points R1, R2, R3 lie on the sidelines of Q1Q2Q3, triangle formed by the intersections of K002 and the circumcircle we shall call the Thomson triangle. More informations below. R1, R2, R3 also lie on :
Obviously, the lines GQi and KRi are parallel. Q1, Q2, Q3 also lie on each rectangular hyperbola of the pencil generated by :
G is the orthocenter of Q1Q2Q3 hence (H1) is the Jerabek hyperbola of Q1Q2Q3. See a generalization in : How pivotal cubics intersect the circumcircle The tangents at these points Q1, Q2, Q3 concur at X on the lines X(2)X(1350) and X(64)X(631). X is the Lemoine point of the Thomson triangle Q1Q2Q3. The first coordinate of X is : a^2[a^2(2b^2+2c^2+a^2)3(b^2+c^2)^220b^2c^2]. Its SEARCH number is : 3.2990623265. The two triangles Q1Q2Q3 and R1R2R3 are perspective at Y on the lines X(6)X(376) and X(39)X(631) with first coordinate : 3a^2(a^2+4b^2+4c^2)+(b^2c^2)^2 and SEARCH number : 1.3852076515 

Thomson cubic and Steiner inellipse 

The tangents at R1, R2, R3 to K002 concur at H. 

The Thomson triangle 

Recall that we call Thomson triangle the triangle T whose vertices are the three points where the Thomson cubic meets the circumcircle of ABC again. Here is a list of properties of this triangle, some of them already mentioned above.
More informations here. 
