X(1), X(3), X(4), X(46), X(90), X(155), X(254), X(371), X(372), X(485), X(486), X(487), X(488), X(6212), X(6213), X(8946), X(8947), X(8948), X(8949)
vertices of orthic triangle
six intersections of a perpendicular bisector and the circle with diameter the corresponding side of ABC i.e. the centers of the six squares erected externally or internally on the sides of ABC
A', B', C' on the circumcircle and the midpoints A1, B1, C1 of A'B'C'.
X3-OAP points, see Table 53 and their isogonal conjugates
The Orthocubic is the isogonal pK with pivot H = X(4). See Table 27. It is also the isogonal pK with pivot O with respect to the orthic triangle.
It is a member of the class CL043 : it meets the circumcircle at A, B, C and three other points A', B', C' where the tangents are concurrent at the point X(25). See further details below and also Q063. The orthocubic of A'B'C' is K376. K006 is also related with the stelloid Q083.
Locus properties :
Asymptotes and related topics
The asymptotes of K006 are parallel to the Simson lines passing through O.
These Simson lines are those of the three points A", B", C" on (O) and on the hyperbola (J1) which is the image of the Jerabek hyperbola (J) under the translation mapping H onto O.
The reflections A', B', C' of A", B", C" about O are the intersections of (O) and K006. More details below.
The Simson lines meet K006 again at three points A1, B1, C1 which are the midpoints of A'B'C' and also the midpoints of HA", HB", HC" and therefore lying on the nine point circle and on the rectangular hyperbola (J2), the homothetic of (J1) under h(H, 1/2).
(J1) contains : X(3), X(20), X(74), X(2574), X(2575)
(J2) contains : X(3), X(5), X(125), X(182), X(2574), X(2575)
Intersection with the circumcircle
Recall that the points A', B', C' are the intersections (apart A, B, C) of K006 and the circumcircle. These points lie on several remarkable rectangular hyperbolas :
• (H1) passing through X(3), X(4), X(110), X(155), X(1351), X(1352), X(2574), X(2575),
• (H2) passing through X(4), X(76), X(99), X(376), X(487), X(488),
• the polar conic of X(25) passing through X(4), X(112), X(371), X(372), X(378), X(1064).
These form a pencil and each hyperbola meets K006 at H, A', B', C' and two other points which are H-Ceva conjugates.
ABC and A'B'C' both circumscribe the MacBeath inconic with foci O and H.
These triangles share the same Euler line and the same nine point circle.
The centers of the three osculating circles at A, B, C to this cubic are collinear on the trilinear polar of X(847).
More generally, the locus of the pivots of all isogonal pKs with the same property is the nonic Q031.
Polar conics of A, B, C
Let (A), (B), (C) be the polar conics of A, B, C in K006
Denote by Oa, Ob, Oc their respective centers.
The isogonal conjugate Oa* of Oa is the intersection of the line AX(264) and the parallel at O to BC with coordinates :
a^2 SA : c^2 SC : b^2 SB
The triangles ABC and OaObOc are triply perspective at X(184), E1 and E2. These two latter points are the orthocorrespondents of the Brocard points Ω1 and Ω2.
Note that OaObOc is also triply perspective with the cevian anticevian, circumcevian triangles of the Lemoine point K.
Furthermore, OaObOc is perspective
• with the cevian triangle of any point on pK(X184 x X1987, X1987) passing through X(3), X(6), X(184), X(217), X(237), X(436), X(1298), X(1987) and X(4) x X(401),
• with the anticevian triangle of any point on pK(X25, X4 x X401) passing through X(4), X(6), X(98), X(184), X(232), X(1987), X(2052), X(3164) and X(4) x X(401).
In both cases, the locus of the perspector is pK(X25, X436) passing through X(2), X(25), X(51), X(184), X(275), X(436), X(1988), X(2052), X(3168).
The two former cubics generate a pencil that contains a third pK namely pK(X6 x X1971, X184) passing through X(6), X(54), X(184), X(1971), X(1976), X(1987) and X(4) x X(401).
The three cubics contain A, B, C, X(6), X(184), X(1987), X(4) x X(401) and two imaginary points on the circumcircle and on the Lemoine axis.
These properties are generalized in CL059.
Lemoine circles in the Orthocubic
There is one (and only one) point whose polar conic in K006 is a circle and this point is K. K006 is the only pivotal isogonal cubic having this property.
This polar conic is the circle with center X(647) orthogonal to the circumcircle.
The parallels to the asymptotes of K006 passing through K meet K006 again at six points that lie on a circle (C) whose center O1 is the midpoint of K, X(647). This circle is orthogonal to the circle with center O and radius R√(1-tan2Ω) where Ω is the Brocard angle.
This circle (C) is analogous to the first Lemoine circle obtained when K006 is replaced by the cubic which is the union of the sidelines of ABC.
The asymptotes of K006 are now reflected about K giving three other lines meeting K006 again at six other points lying on a same circle with center O2.
This circle is analogous to the second Lemoine circle obtained when K006 is replaced by the cubic which is the union of the sidelines of ABC.
Tucker circles in the Orthocubic
The properties above can be generalized as follows. The homothety with center X(6), ratio k, transforms the asymptotes of K006 into three lines meeting K006 again at six points lying on a same circle which is analogous to a Tucker circle.
The values k = 0, k = -1 give the two Lemoine circles above.
When k = 1, we obtain the satellite of the line at infinity since the circle must decompose.
All these circles have their centers on the line X(6), X(647) which is in some way the Brocard axis of the cubic K006.