Sunday, September 8, 2013

Interesting locus: Conic through 34 ETC centers


What is the locus of P such that the anticevian triangle of P w/r to ABC is perspective to the intangents triangle of ABC?
The answer is:
1) The antiorthic axis of ABC, line (X(44)X(513)), with trilinear equation u+v+w = 0, or
2) The circumhyperbola U with trilinear equation
U: ∑ [ a*(b-c)*(b+c-a)*v*w ] = 0
The perspector of U is X(663).
The center of U is:
a*(b-c)^2*(b+c-a)*(a^3-2*(b+c)*a^2+(b^2+b*c+c^2)*a-b*c*(b+c)) : :
and lies on lines (X(I)X(J)) for these (I,J): (41,4557), (649,4014), (657,3271), (1200,2246), (3124,5075)      
U pasess through A, B, C and these 34 ETC centers: X(6), X(9), X(19), X(55), X(57), X(284), X(333), X(673), X(893), X(909), X(1024), X(1174), X(1436), X(1751), X(1945), X(2160), X(2161), X(2164), (2195), X(2258), X(2259), X(2291), X(2299), X(2316), X(2319), X(2337), X(2339), X(2343), X(2364), X(2432), X(2590), X(2591), X(3451), X(3512) 

Mappings:
1) If P is on the antiorthic axis of ABC then the perspector Z(P) lies on line (X(650)X(663)) with trilinear equation: u/(s-a)+v/(s-b)+w/(s-c)=0. This line passes through this 15 ETC-centers: X(650), X(663), X(861), X(2340), X(3689), X(3900), X(4041), X(4105), X(4162), (4433), X(4435), X(4477), X(4814), X(4895), X(4959)
There are 92 known ETC centers on the antiorthic axis (up to X(5546)) and for only two of them the correspondant perspectors are defined in ETC. These [ P, Z(P) ] are [X(650), X(4162)] and [X(652), X(663)].
You can see/download the mapping from this part of the locus in table 1 and table 1.2 at end of this page, [Note: most of pairs (P, Z(P)) are not easy to handle and only the most simple ones has been calculated.]

2) If P lies on conic U, then the perspectors Z(P) lie on the hyperbola V with trilinear equation:
V: ∑ [ a*(b-c)*(b+c-a)^2*v*w ] = 0
The perspector of V is X(657).
The center of V has trilinears:
a*(b-c)^2*(-a+b+c)^2*(a^2*(a^2-b^2+b*c-c^2)-a*(b+c)*(-b^2-c^2+a^2)-b*c*(b-c)^2) : :
or, equivalently:
cos(A/2)^2*(cos(2*A)+r/R+3)*sin(B/2-C/2)^2 : :
and lies on lines (X(I)X(J)) for these (I,J): (1,4566), (11,3138), (663,3022), (997,4319), (1015,3269), (1064,2293), (1984,2310)
The hyperbola V passes through A, B, C and these 14 ETC centers: X(1), X(33), X(55), X(64), X(103), X(200), X(220),X(963), X(1043), X(2192),X(2328), X(2332), X(2342), X(4845).
For P on cubic U, (P, Z(P)) = (X(I),X(J)) for these [I,J]:   [6, 55], [9, 200], [19, 33], [55, 220], [57, 1], [284, 2328], [333, 1043], [909, 2342], [1436, 2192], [2291, 4845], [2299, 2332] .
Please see/download tables 2.1 and 2.2  for complete lists of points and perspectors.

  Direct mapping for P on antiorthic axis   Download
  Inverse mapping for Z(P) on line (X(650)X(663))   Download
  Direct mapping for P on conic U   Download
  Inverse mapping for Z(P) on conic V   Download

Note: Show tables seems to work well only with Google Chrome.

Saturday, September 7, 2013

Nice trilinear coordinates

The sum and difference of two simple terms were applied to the ETC search triangle (6,9,13). The resulting numerical coordinates were sought in the ETC tables and then they were checked algebraically.

SA, SB, SC, SW are the standard variables for Conway notation.
S=2*area(ABC), R=circumradius, r=inradius and s=semiperimeter of triangle.

X(7) (b*c-SA)/a X(610) SB*SC-a^2*SA X(2223) a^2*(a*s-SW)
X(8) (b*c+SA)/a X(612) b*c+SW X(2285) SB*SC+a^2*b*c
X(9) a-s X(614) b*c-SW X(2300) a^2*(a*s+SA)
X(19) a^2*SA-S^2 X(615) a*R-b*c X(2308) a*(a*r+S)
X(37) a*r-S X(661) SB-SC X(2548) a^3*R+b*c*S
X(38) SA+SW X(672) a*(a*s-SW) X(2964) a^2-R^2
X(41) a^2*(a-s) X(748) a^2*r*s-b*c*S X(2965) a*(a^2-R^2)
X(42) a*(a*r-S) X(750) a^2*r*s+b*c*S X(2999) b*c-s^2
X(47) a^2*r*s-S*R^2 X(798) SB^2-SC^2 X(3053) a*(a^2-SA)
X(48) SB*SC-S^2 X(894) (b*c+a^2)/a X(3068) (S+a^2)/a
X(55) a*(a-s) X(940) a*s+b*c X(3069) (S-a^2)/a
X(57) SA-b*c X(968) a^2*r-S*s X(3083) b*c+S
X(58) a^2*s+S*R X(1100) a*r+S X(3084) b*c-S
X(63) SA X(1124) a*(S+b*c) X(3299) a+R
X(75) SA^2+S^2 X(1193) a*(a*s+SA) X(3301) a-R
X(77) SA*(SA-b*c) X(1203) a*s-R*r X(3553) a*R+r*s
X(78) SA*(SA+b*c) X(1267) (b*c+S)/a X(3553) a^2*b*c+S^2
X(171) a^2+b*c X(1335) a*(S-b*c) X(3554) a*R-r*s
X(191) SA+R*r X(1386) a*s+SW X(3554) a^2*b*c-S^2
X(193) (SA-a^2)/a X(1449) a+s X(3624) b*c+R*r
X(213) a^2*(a*r-S) X(1468) a*(a*s+b*c) X(3666) SA+a*s
X(238) a^2-b*c X(1572) a^3*s+S^2 X(3751) a*S-SW*r
X(239) (b*c-a^2)/a X(1580) a^4-b^2*c^2 X(3915) a*(a*s-b*c)
X(326) b^2*c^2-S^2 X(1582) a^4+b^2*c^2 X(4258) a*(a^2-s^2)
X(405) b*c*S+SA*r*a X(1698) b*c-R*r X(4383) a*s-b*c
X(474) b*c*S-SA*r*a X(1707) a^2-SA X(4512) a^2-s^2
X(491) (SA-S)/a X(1743) a*S-s^2*r X(4641) SA-a*s
X(492) (SA+S)/a X(1953) SB*SC+S^2 X(5019) a^2*(a*s+b*c)
X(518) a*s-SW X(1958) SA^2+SB*SC X(5058) a^2*(a*R-b*c)
X(560) a^2*(SA-SW) X(1958) a^2*SA-b^2*c^2 X(5062) a^2*(a*R+b*c)
X(590) a*R+b*c X(1959) SA^2-SB*SC X(5266) SA*r*a-S*SW
X(595) a^2*s-S*R X(1964) SA^2-SW^2 X(5277) a^3*r+b*c*S
X(604) a^2*(SA-b*c) X(1964) a^2*(SA+SW) X(5280) a*SW+S*R
X(605) a^2*(S+b*c) X(2082) SB*SC-a^2*b*c X(5299) a*SW-S*R
X(606) a^2*(S-b*c) X(2175) a^3*(a-s) X(5336) SB*SC-a^3*s
X(609) a^3+S*R X(2210) a^2*(a^2-b*c) X(5391) (b*c-S)/a

Sunday, August 25, 2013

Parallel and perpendicular central lines



Central lines determined by 8-first ETC centers have many parallel and perpendicular central lines. 

These results have been found using ETC centers X(1)-X(5543) as published by August 25th, 2013.

Note: The line at infinity ∞ is both parallel and perpendicular to any line and has been removed from all lists.


NAGEL LINE (X(1), X(2))=(IG)
  • Parallel lines intersecting L­ at X(519):  
  • Perpendicular lines intersecting  at X(3667):

EULER LINE (X(2), X(3))=(GO)
  • Parallel lines intersecting  at X(30):
  • Perpendicular lines intersecting  at X(523):

SODDY LINE (X(1), X(7))=(IGe)
  • Parallel lines intersecting  at X(516):
  • Perpendicular lines intersecting  at X(514):

LINE (X(1), X(3))=(IO)
  • Parallel lines intersecting  at X(517):
  • Perpendicular lines intersecting  at X(513):

BROCARD AXIS (X(3), X(6))=(OK)
  • Parallel lines intersecting  at X(511):
  • Perpendicular lines intersecting  at X(512):

LINE (X(1), X(4))=(IH)
  • Parallel lines intersecting  at X(515):
  • Perpendicular lines intersecting  at X(522):

LINE (X(1), X(5))=(IN)
  • Parallel lines intersecting  at X(952):
  • Perpendicular lines intersecting  at X(900):

LINE (X(1), X(6))=(IK)
  • Parallel lines intersecting  at X(518):
  • Perpendicular lines intersecting  at X(3309):

LINE (X(2), X(6))=(GK)
  • Parallel lines intersecting  at X(524):
  • Perpendicular lines intersecting  at X(1499):

LINE (X(2), X(7))=(GGe)
  • Parallel lines intersecting  at X(527):
  • Perpendicular lines intersecting  at X(?) (see [1] below):

LINE (X(3), X(7))=(OGe)
  • Parallel lines intersecting  at X(?) (see [2] below):
  • Perpendicular lines intersecting  at X(?) (see [3] below):

LINE (X(3), X(8))=(ONa)
  • This line is parallel to line (X(1), X(5) ) = (IN) 

LINE (X(4), X(6))=(HK)
  • Parallel lines intersecting  at X(1503):
  • Perpendicular lines intersecting  at X(525):

LINE (X(4), X(7))=(HGe)
  • Parallel lines intersecting  at X(971):
  • Perpendicular lines intersecting  at X(3900):

LINE (X(4), X(8))=(HNa)
  • This line is parallel to line (X(1), X(3))=(IO)

LINE (X(5), X(6))=(NK)
  • Parallel lines intersecting  at X(3564):
  • Perpendicular lines intersecting  at X(3566):

LINE (X(5), X(7))=(NGe)
  • Parallel lines intersecting  at X(?) (see [4] below):
  • Perpendicular lines intersecting  at X(?) (see [5] below):

LINE (X(5), X(8))=(NNa)
  • Parallel lines intersecting  at X(?) (see [6] below):
  • Perpendicular lines intersecting  at X(?) (see [7] below):

LINE (X(6), X(7))=(KGe)
  • Parallel lines intersecting  at X(?) (see [8] below):

LINE (X(6)X(8))=(KNa)
  • Parallel lines intersecting  at X(?) (see [9] below):
  • Perpendicular lines intersecting  at X(?) (see [10] below):

LINE (X(7), X(8))=(GeNa)
  • This line is parallel to line (X(1), X(6))=(IK)

NOTES Non-ETC intersections:  (All barycentrics)

[1]: (b-c)*(3*a^3-(5*(b+c))*a^2+(b+c)^2*a+(b+c)*(b-c)^2) : :
[2]: 2*a^6-(2*(b+c))*a^5-(3*(b^2+c^2))*a^4+(2*(b+c))*(b^2+c^2)*a^3+(2*(b^3-c^3))*(b-c)*a^2-(b^2-c^2)^2*(b-c)^2 : :

[3]: (b-c)*(2*a^3-(3*(b+c))*a^2+(b^2-c^2)*(b-c)) : :

[4]: 2*a^6+(-7*c^2-7*b^2+4*b*c)*a^4+(2*(b+c))*(b^2+c^2)*a^3+(6*(b^3-c^3))*(b-c)*a^2-2*(b-c)^2*(b+c)^3*a-(b^2-c^2)^2*(b-c)^2 : :

[5]: (b-c)*(4*a^3-(7*(b+c))*a^2+2*(b+c)^2*a+(b^2-c^2)*(b-c)) : :

[6]: 2*a^4-(4*(b+c))*a^3-(c^2+b^2-8*b*c)*a^2+(4*(b^2-c^2))*(b-c)*a-(b^2-c^2)^2 : :

[7]: (b-c)*(b+c-4*a) : :

[8]: 2*a^4-(2*(b+c))*a^3+a^2*(b^2+c^2)-(b^2+c^2)*(b-c)^2 : :

[9]: 2*a^3+(b^2+c^2)*a-(b+c)*(b^2+c^2) : :

[10]: (b-c)*(2*a^3+(b+c)*a^2+(2*(b^2+c^2))*a-(b+c)*(b^2+c^2)) : :