Locus

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• Let ABC be a triangle and A B C the cevian / pedal triangle of a point P. Denote: Ab, Ac:=The orthogonal projections of B ,C on PC ,PB , resp. A := B C /
Message 1 of 240 , May 1, 2009
Let ABC be a triangle and A'B'C' the cevian / pedal
triangle of a point P.

Denote:
Ab, Ac:=The orthogonal projections of B',C' on PC',PB',
resp.

A":= B'C' /\ AbAc.

Similarly Bc,Ba, B" and Ca,Cb, C".

Which is the locus of P such that:

1. AbAc, BcBa, CaCb are concurrent

2. A",B",C" are collinear.

APH
• [APH]: Let ABC be a triangle. A line L passing through A intersects the circle with diameter AB again at Ab and the circle with diameter AC again at Ac.
Message 240 of 240 , Feb 16

[APH]:

Let ABC be a triangle.

A line L passing through A intersects the circle with diameter AB again at Ab and the circle with diameter AC again at Ac.

[Equivalently: Let Ab, Ac be the orthogonal projections of B, C on L, resp.]
Let A* be the intersection of BAc and CAb.

Which is the locus of A* as L moves around A?

Parametric trilinear equation:

1/u(t) = a*((b^2+c^2-a^2)^2-4*b^2*c^2*c os(2*t)^2)/(2*S)

1/v(t) = 2*(cos(2*t)*c-b)*S - c*sin(2*t)*(a^2+3*b^2-2*cos(2* t)*b*c-c^2)

1/w(t) = 2*(cos(2*t)*b-c)*S + b*sin(2*t)*(a^2+3*c^2-2*cos(2* t)*b*c-b^2)

Regards,