This continuation of Points on Cubics is devoted to one class of cubics. Access to related material is provided at the bottom of this page. POINTS ON CUBICS
ZP(U,P): Z-Plus Cubics,
defined by
upx(qy2 + rz2) + vqy(rz2 + px2) + wrz(px2 + qy2) = 0
Notes about ZP Cubics:
1. ZP(U,P) is also given by
(vqy + wrz)px2 + (wrz + upx)qy2 + (upx + vqy)rz2 = 0. 2. In Jean-Pierre Ehrmann and Bernard Gibert, "Special Isocubics in the Triangle Plane," downloadable from Cubics in the Triangle Plane, the cubics ZP-cubics are denoted by nK0.3. A subclass of cubics ZP(U,P) are mentioned in TCCT (1998, p. 241) as self-isogonal conjugate cubics. There, for example, ZP(X(513),X(1)) is denoted by Z+(L), where L denotes the line X(1)X(6). In order to reconcile the present notation with the earlier, note that X(513) is the point whose trilinears, b - c : c - a : a - b, are the coefficients of the line X(1)X(6); i.e., X(513) is the crossdifference of X(1) and X(6).
4. As suggested in Note 3, it is useful to regard each U in the list of cubics ZP(U,P) as representative of the central line, any two of whose points have crossdifference U. The following list gives, for selected centers U, the corresponding line X(I)X(J):
U = X(1) represents the line X(44)X(513)
U = X(6) represents the line X(30)X(511), the line at infinity
U = X(244) represents the line X(100)X(101)
U = X(512) represents the line X(2)X(6)
U = X(513) represents the line X(1)X(6)
U = X(520) represents the line X(1)X(6)
U = X(523) represents the line X(3)X(6), the Brocard axis
U = X(647) represents the line X(2)X(3), the Euler line
U = X(647) represents the line X(2)X(3)
U = X(649) represents the line X(1)X(2)
U = X(650) represents the line X(1)X(3)
U = X(652) represents the line X(1)X(4)5. Z(U,P) is the set of points X for which a collinearity-determinant is zero; ZP(U,P) is the set of points X for which the corresponding permanent is zero. (The permanent is sometimes called "plus-determinant", as it results from changing the minus signs in the definition of determinant to plus signs.)
6. These three points are on ZP(U,P):
vwqr(v2q - w2r) : - wurp(v2q + w2r) : uvpq(v2q + w2r), 7. The discriminant d of ZP(U,P), obtained by solving the defining equation for x in terms of y and z, under the assumption that X does not satisfy vqy + wrz = 0, is given byvwqr(w2r + u2p) : wurp(w2r - u2p) : - uvpq(w2r + u2p),
- vwqr(u2p + v2q) : wurp(u2p + v2q) : uvpq(u2p - v2q).
d2 = u2p2(qy2 + rz2)2 - 4pqryz(wy + vz)(vqy + wrz). The discriminant can be used to show that the following six points are on ZP(U,P):0 : v : - w - u : 0 : w u : - v : 0, 8. Suppose that F = f : g : h is a triangle center. The collineation X --> F*X that carries each point x : y : z to the trilinear product fx : gy : hz also carries the cubic ZP(U,P) onto the the cubic ZP(F*U,P*F -2).u(v2q + w2r) : v(w2r - v2q) : - w(w2r - v2q)
- u(u2q - w2r) : v(w2r + u2p) : w(u2p - w2r)
u(v2q - u2p) : - v(v2r - u2p) : w(u2p + v2q)
ZP(X(1),X(244)) passes through these centers:
100, 813, 1023, 1025, 2p901, 6p874, 8p919, 100p1931, 101p447, 190p2054, 545p901Collinear triple
1023 2p901 545p901 ZP(X(2),X(292)) passes through these centers:
1, 190, 239, 659, 2p1023, 88p659Collinear triples
1 239 2p1023 190 659 2p1023 ZP(X(3),X(651)) passes through these centers:
1, 6, 522, 650, 8p2183, 104p513, 523p1822, 523p1823, 650p1113, 65pp1114Collinear triples
1 6 8p2183 1 522 104p513 6 650 104p513 6 523p1822 650p1113 6 523p1823 650p1114 522 650 8p2183 522 523p1822 523p1823 522 650p1113 650p1114 ZP(X(3),X(662)) passes through these centers:
6, 325, 523, 19p878, 523p1822, 523p1823, 661p1113, 661p1114Collinear triples
6 523 19p878 6 523p1822 661p1113 6 523p1823 661p1114 523 523p1822 523p1823 523 661p1113 661p1114 ZP(X(4),X(296)) passes through these centers:
1, 243, 653, 108p527, 243p652Collinear triples
1 243 108p527 653 108p527 243p652 ZP(X(5),X(655)) passes through these centers:
1, 523. 654. 36p294ZP(X(6),X(244)) passes through these centers:
100, 660, 898, 31p874, 100p899, 100p2107, 190p2106, 422p1331, 537p901Collinear triples
660 100p899 537p901 898 31p874 537p901 ZP(X(6),X(291)) passes through these centers:
1, 100, 238, 659, 100p899, 739p812Collinear triples
1 238 100p899 100 659 100p899 ZP(X(6),X(658)) passes through these centers:
55, 241, 650, 200p884, 650p1381, 650p1382Collinear triples
55 650 200p884 650 650p1381 650p1382 ZP(X(9),X(11)) passes through these centers:
100, 109, 677, 59p676, 100p1155, 109p1156, 144p1461Collinear triples
100 109 100p1155 100 677 144p1461 109 59p676 144p1461 ZP(X(9),X(101)) passes through these centers:
1, 514, 1027, 2p518, 514p1381, 514p1382, 522p1381, 522p1382Collinear triples
1 514 1027 1 514p1381 522p1381 1 514p1382 522p1382 514 514p1381 514p1381 514 522p1381 522p1382 ZP(X(9),X(105)) passes through these centers:
1, 100, 518, 2254, 88p1642, 100p1155, 518p1381, 518p1382, 519p840, 522p1381, 522p1382, 665p1121Collinear triples
1 100 88p1642 1 518 100p1155 1 2254 519p840 1 518p1381 522p1381 1 518p1382 522p1382 100 518 519p840 100 2254 100p1155 518 2254 88p1642 518 518p1381 518p1382 518 522p1382 522p1382 ZP(X(9),X(106)) passes through these centers:
1, 519, 1026, 105p900, 519p1381, 519p1382, 522p1381, 522p1382Collinear triples
1 519 1026 1 519p1381 522p1381 1 519p1382 522p1382 519 519p1381 519p1382 519 522p1381 522p1382 ZP(X(19),X(293)) passes through these centers:
1, 162, 240, 4p684, 30p842, 110p468, 240p1822, 240p1823, 523p1113, 523p1114, 691p868Collinear triples
1 240 110p468 1 4p684 30p842 1 240p1822 523p1113 1 240p1823 523p1114 162 240 30p842 162 4p684 110p468 240 240p1822 240p1823 240 523p1113 523p1114 ZP(X(21),X(662)) passes through these centers:
1, 6, 523, 661, 10p2245, 513p759, 523p1379, 523p1380, 523p1822, 523p1823, 661p1113, 661,1114Collinear triples
1 6 10p2245 1 523 513p759 6 661 513p759 6 523p1822 661p1113 6 523p1823 661p1114 523 661 10p2245 523 523p1822 523p1823 523 661p1113 661p1114 661 523p1379 523p1380 ZP(X(25),X(336)) passes through these centers:
6, 112, 232, 19p684, 112p896, 232p1822, 232p1823, 661p1113, 661p1114, 842p2173Collinear triples
6 232 112p896 6 19p684 842p2173 6 232p1822 661p1113 6 232p1823 661p1114 112 232 842p2173 112 19p684 112p896 232 232p1822 232p1823 232 661p1113 661p1114 ZP(X(35),X(651)) passes through these centers:
1, 37, 650, 2323, 9p1019, 11p2222Collinear triples
1 37 2323 1 9p1019 11p2222 37 650 11p2222 650 2323 9p1019 ZP(X(44),X(1)) passes through these centers:
1, 100, 513, 100p537, 101p545, 109p528, 522p840, 527p919, 536p813, 665p1121, 739p812Collinear triples
100 513 101p545 100 100p537 739p812 100 109p528 665p1121 100 522p840 527p919 513 100p537 536p813 513 109p528 527p919 513 522p840 665p1121 ZP(X(55),X(190)) passes through these centers:
6, 513, 518, 6p1027, 513p1381, 513p1382, 650p1381, 650p1382Collinear triples
6 513 6p1027 6 513p1381 650p1381 6 513p1382 650p1382 513 513p1381 513p1382 513 650p1381 650p1382 ZP(X(57),X(294)) passes through these centers:
1, 241, 651, 2254, 44p651, 88p2254, 514p1381, 514p1382, 518p1381, 518p1382, 527p840Collinear triples
1 241 44p651 1 2254 527p840 1 514p1381 518p1381 1 514p1382 518p1382 241 651 527p840 241 514p1381 514p1382 241 518p1381 513p1382 651 2254 44p651 ZP(X(100),X(657)) passes through these centers:
7, 651, 883, 1462, 2p1381, 2p1382, 7p1381, 7p1382Collinear triples
7 651 1462 7 2p1381 2p1382 7 7p1381 7p1382 651 2p1381 7p1381 651 2p1382 7p1382 ZP(X(101),X(522)) passes through these centers:
1, 109, 1381, 1382, 104p999Collinear triples
1 109 104p999 1 1381 1382 ZP(X(105),X(241)) passes through these centers:
1, 294, 650, 2p919, 9p1022, 9p1381, 9p1382, 105p1023, 528p2291, 885p1381, 885p1382Collinear triples
1 294 105p1023 1 650 528p2291 1 9p1381 9p1382 1 885p1381 885p1382 294 2p919 528p2291 294 9p1381 885p1381 294 9p1382 885p1382 650 2p919 105p1023 ZP(X(109),X(514)) passes through these centers:
1, 101, 1381, 1382, 7p2283, 9p1381, 9p1382, 9p2195Collinear triples
1 101 9p2195 1 1381 1382 1 9p1381 9p1382 101 1381 9p1381 101 1382 9p1382 ZP(X(109),X(655)) passes through these centers:
101, 1381, 1382, 11p36Collinear triple
1381 1382 11p36 ZP(X(109),X(666)) passes through these centers:
101, 1381, 1382, 11p1458Collinear triple
1381 1382 11p1458 ZP(X(110),X(656)) passes through these centers:
2, 112, 1113, 1114Collinear triple
2 1113 1114 ZP(X(112),X(656)) passes through these centers:
4, 110, 1113, 1114, 1302p1725Collinear triple
1 1113 1114 ZP(X(112),X(661)) passes through these centers:
2, 110, 1113, 1114, 2p1822, 2p1823, 3p293, 19p877Collinear triples
2 110 3p293 2 1113 1114 2 2p1822 2p1823 110 1113 2p1822 110 1114 2p1823 ZP(X(238),X(2)) passes through these centers:
1, 6, 100, 649, 101p537, 106p899, 519p739Collinear triples
1 6 101p537 1 100 106p899 1 649 519p739 6 100 519p739 6 649 106p899 100 649 101p637 ZP(X(239),X(6)) passes through these centers:
1, 2, 190, 513, 88p899, 100p537, 889p1960Collinear triples
1 2 100p537 1 190 889p1960 1 513 88p899 2 190 88p899 2 513 889p1960 190 513 100p537 ZP(X(240),X(63)) passes through these centers:
1, 19, 162, 661, 30p111, 74p468, 110p1312, 110p1313, 112p542, 112p1312, 112p1313, 523p842Collinear triples
1 19 112p542 1 162 74p468 1 661 30p111 19 162 30p111 19 661 74p468 162 661 112p542 162 110p1312 110p1313 162 112p1312 112p1313 661 110p1312 112p1312 661 110p1313 112p1313 ZP(X(241),X(9)) passes through these centers:
1, 57, 513, 651, 88p1155, 109p528, 514p840, 1121p1404Collinear triples
1 57 109p528 1 513 88p1155 1 651 1121p1404 57 513 1121p1404 57 651 88p1155 513 651 109p528 ZP(X(297),X(48)) passes through these centers:
2, 4, 523, 648, 30p897, 162p542, 162p1312, 468p2349, 662p1312, 842p1577Collinear triples
2 4 162p542 2 523 30p897 2 648 468p2349 4 523 468p2349 4 648 30p897 523 648 162p542 523 162p1312 662p1312 ZP(X(350),X(42)) passes through these centers:
2, 75, 514, 668, 88p536, 190p537, 889p1635Collinear triples
2 75 190p537 2 514 88p536 2 668 889p1635 75 514 889p1635 75 668 88p536 514 668 190p537 ZP(X(385),X(1)) [Brocard (first) cubic, K017] passes through these centers:
2, 6, 99, 512, 111p2234Collinear triples
2 99 111p2234 6 512 111p2234 ZP(X(401),X(19)) passes through these centers:
2, 3, 520, 648, 852p2349Collinear triples
2 648 852p2349 3 520 852p2349 ZP(X(450),X(1)) passes through these centers:
3, 4, 647, 648, 852p897Collinear triples
3 647 852p897 4 648 852p897 ZP(X(511),X(92)) passes through these centers:
3, 6, 110, 647, 74p896, 110p2247, 163p1312, 163p1313, 656p842, 895p2173Collinear triples
3 6 110p2247 3 110 74p896 3 647 895p2173 6 110 895p2173 6 647 74p896 110 647 110p2247 110 163p1312 163p1313 ZP(X(512),X(31)) passes through these centers:
2, 385, 538, 1916, 10p2106, 75p729, 274p2107, 297p1957 (no collinearities found)ZP(X(512),X(75)) passes through these centers:
6, 111, 187, 232, 248, 385, 2p1927, 6p1757, 6p1758, 6p1929, 13p2152, 14p2151, 19p450, 48p1942, 71p422, 74p2247, 82p2076, 421p1820, 425p1400, 543p923, 842p2173, 843p896, 2080p2186Collinear triples
111 187 543p923 111 232 74p2247 111 248 842p2173 187 232 842p2173 187 248 74p2247 13p2152 14p2151 74p2247 ZP(X(513),X(1)) [ K137] passes through these centers:
1, 44, 88, 239, 241, 292, 294, 1931, 2p2054, 6p447, 106p545, 527p840, 528p2291, 537p739, 1280p1743Collinear triples
44 88 106p545 44 241 527p840 44 292 537p739 44 294 528p2291 88 239 537p739 88 241 528p2291 88 294 527p840 ZP(X(513),X(8)) passes through these centers:
6, 57, 2291, 6p1323, 13p2307, 15p2306, 554p2152, 559p2154Collinear triples
6 57 6p1323 6 13p2307 559p2154 6 15p2306 554p2152 57 13p2307 554p2152 57 15p2306 559p2154 ZP(X(514),X(31)) passes through these centers:
2, 291, 350, 447, 519, 2p241, 2p294, 2p1932, 10p1929, 88p545, 145p1280, 528p1156Collinear triples
519 903 88p545 519 2p294 528p1156 903 2p241 528p1156 ZP(X(514),X(55)) passes through these centers:
1, 7, 1156, 1323, 13p1082, 14p559, 15p1081, 16p554Collinear triples
1 7 1323 1 13p1082 14p559 1 15p1081 16p554 7 13p1082 16p554 7 14p559 15p1081 ZP(X(514),X(81)) passes through these centers:
2, 42, 55, 226, 519, 672, 10p105, 37p106Collinear triples
2 42 519 2 55 10p105 2 226 672 42 55 672 42 226 10p105 ZP(X(518),X(57)) passes through these centers:
1, 9, 100, 650, 44p1156, 100p2246, 522p840, 527p2316Collinear triples
1 9 100p2246 1 100 527p2316 1 650 44p1156 9 100 44p1156 9 650 527p2316 100 650 100p2246 ZP(X(520),X(31)) passes through these centers:
2, 401, 1972, 63p450, 92p852, 92p1942, 226p416, 325p1958ZP(X(520),X(92)) passes through these centers:
3, 6, 74, 3p2173Collinear triple
3 6 3p2173 ZP(X(521),X(1)) passes through these centers:
9, 57, 1944, 1945Collinear triple
9 57 1944 ZP(X(521),X(4)) passes through these centers:
1, 3, 2338, 63p1456Collinear triple
1 3 63p1456 ZP(X(521),X(31)) passes through these centers:
2, 448, 1944, 1952, 63p425, 92p416ZP(X(521),X(81)) passes through these centers:
9, 65, 2182, 2331, 10p102, 10p1433Collinear triples
9 2182 10p1433 9 2331 10p1102 65 2182 2331 65 10p102 10p1433 ZP(X(521),X(92)) passes through these centers:
3, 6, 221, 268, 2182, 3p102, 48p1325Collinear triples
3 6 48p1325 3 221 3p102 3 268 2182 6 221 2182 6 268 3p102 ZP(X(522),X(31)) passes through these centers:
2, 527, 673, 1121, 1948, 2p296, 2p518, 63p415, 88p528, 694p1281Collinear triples
527 673 88p528 1121 2p518 88p528 ZP(X(522),X(55)) passes through these centers:
2, 57, 527, 2p103, 2p1456, 7p1419, 7p2291Collinear triples
2 57 527 2 2p103 7p1419 57 2p1456 7p1419 ZP(X(522),X(56)) passes through these centers:
2, 9, 527, 8p2291, 283p1832, 283p1833, 1793p1832, 1793p1833Collinear triples
2 9 527 2 283p1832 1793p1832 2 283p1833 1793p1833 9 283p1832 1793p1833 9 1793p1832 1793p1833 ZP(X(522),X(63)) passes through these centers:
1, 19, 102, 208, 282, 4p2182, 6p1325Collinear triples
1 19 6p1325 1 102 208 1 282 4p2182 19 102 282 19 208 4p2182 ZP(X(522),X(81)) passes through these centers:
1, 19, 102, 208, 282, 4p2182, 6p1325Collinear triples
6 73 2183 6 281 2p2250 10 73 2p2250 10 281 2183 ZP(X(523),X(1)) [a Brocard cubic, K018] passes through these centers:
2, 6, 13, 14, 15, 16, 111, 368, 524, 530p2153, 531p2154Collinear triples
2 6 524 2 13 16 2 14 15 6 13 14 6 15 6 13 15 530p2153 14 16 531p2154 111 530p2153 531p2154 ZP(X(523),X(31)) [ K185] passes through these centers:
2, 287, 297, 524, 671, 694, 2p1757, 2p1758, 2p1929, 2p1966, 63p1942, 92p450, 94p1094, 94p1095, 226p425, 306p422, 542p2349, 543p897Collinear triples
286 524 542p2349 297 671 542p2349 524 671 543p897 94p1094 94p1095 542p2349 ZP(X(523),X(63)) passes through these centers:
4, 6, 74, 1990Collinear triple
4 6 1990 ZP(X(523),X(91)) passes through these centers:
371, 372, 47p94Collinear triple
371 372 47p94 ZP(X(523),X(92)) passes through these centers:
3, 6, 50, 265Collinear triple
3 6 50 ZP(X(524),X(31)) passes through these centers:
2, 99, 523, 162p542, 543p662, 843p1577Collinear triple
99 523 543p662 ZP(X(525),X(19)) passes through these centers:
2, 3, 30, 3p2349Collinear triple
2 3 30 ZP(X(525),X(31)) passes through these centers:
2, 30, 98, 325, 1494, 3p1956, 72p447, 92p401, 226p448, 441p2184, 542p897, 1297p1895Collinear triples
30 98 542p897 325 1494 542p897 ZP(X(525),X(48)) passes through these centers:
2, 4, 30, 4p2349Collinear triple
2 4 30 ZP(X(525),X(63)) passes through these centers:
2, 25, 30, 1073, 1297, 4p204, 4p2159, 4p2312Collinear triples
2 25 30 2 1073 4p2312 2 1297 4p204 25 1073 1297 25 4p204 4p2312 ZP(X(527),X(31)) passes through these centers:
2, 522, 664, 44p666, 88p918, 100p528, 693p840Collinear triples
522 44p666 100p528 522 88p918 693p840 664 44p666 693p840 664 88p918 100p528 ZP(X(528),X(31)) passes through these centers:
2, 666, 918, 7p1023, 8p1022, 100p527, 513p1121Collinear triples
666 7p1023 513p1121 666 8p1022 100p527 918 7p1023 100p527 918 8p1022 513p1121 ZP(X(536),X(31)) passes through these centers:
2, 513, 668, 88p812, 100p537, 335p1023Collinear triples
513 100p537 335p1023 668 88p812 100p537 ZP(X(537),X(31)) passes through these centers:
2, 812, 1022, 2p660, 44p668, 100p536, 693p739Collinear triples
812 1022 693p739 812 44p668 100p536 1022 2p660 100p536 2p660 44p668 693p739 ZP(X(542),X(92)) passes through these centers:
3, 6, 879, 110p1755Collinear triple
3 6 110p1755 ZP(X(647),X(75)) passes through these centers:
6, 74, 511, 1495, 1976, 4p1955, 48p1987, 111p2247, 204p1297, 228p447, 441p2155, 448p1400, 765p866, 842p896Collinear triples
74 511 111p2247 74 1976 842p896 511 1495 842p896 1495 1976 111p2247 ZP(X(647),X(91)) passes through these centers:
371, 372, 511, 24p293Collinear triple
371 372 511 ZP(X(649),X(1)) passes through these centers:
1, 238, 291, 899, 2107, 2p739, 2p2106, 3p422, 105p1983, 106p537, 1463p2053Collinear triples
238 2p739 106p537 291 899 106p537 511 1495 842p896 1495 1976 111p2247 ZP(X(649),X(58)) passes through these centers:
1, 10, 726, 899, 2p192, 10p727, 37p2162, 321p739Collinear triples
1 10 899 1 726 37p2162 1 2p192 10p727 10 726 2p192 10 10p727 37p2162 ZP(X(649),X(75)) passes through these centers:
6, 106, 238, 902, 1326, 1458, 1911, 2054, 2195, 31p447, 840p1155, 2246p2291Collinear triples
106 1458 2246p2291 106 2195 840p1155 902 1458 840p1155 902 2195 2246p2291 ZP(X(650),X(1)) [Pelletier strophoic, K040] passes through these centers:
1, 105, 243, 296, 518, 1155, 1156, 3p415, 80p202, 80p203, 88p2246, 519p840, 1281p1967Collinear triples
105 1155 80p2246 105 1156 519p840 518 1155 519p840 518 1156 80p2246 80p202 80p203 80p2246 ZP(X(650),X(7)) passes through these centers:
1, 55, 1155, 9p2291, 13p1250, 15p1251, 1833p2193Collinear triples
1 55 1155 1 13p1250 1833p2193 55 15p1251 1833p2193 ZP(X(650),X(8)) passes through these centers:
1, 56, 103, 1155, 1456, 56p1156, 57p1419Collinear triples
1 56 1155 1 103 57p1419 56 1456 57p1419 ZP(X(652),X(1)) passes through these centers:
1, 1936, 1937, 3p425, 4p416, 6p448ZP(X(652),X(75)) passes through these centers:
55, 56, 1936, 6p1945Collinear triple