TriangleCurve Command
 TriangleCurve( <Point P>, <Point Q>, <Point R>, <Equation in A, B, C> )

Creates implicit polynomial, whose equation in barycentric coordinates with respect to points P, Q, R is given by the fourth parameter; the barycentric coordinates are referred to as A, B, C.
If P, Q, R are points, TriangleCurve(P, Q, R, (A  B)*(B  C)*(C  A) = 0)
gives a cubic curve consisting of
the medians of the triangle PQR.
TriangleCurve(A, B, C, A*C = 1/8)
creates a hyperbola such that tangent, through A or C, to this hyperbola
splits triangle ABC in two parts of equal area.
TriangleCurve(A, B, C, A² + B² + C²  2B C  2C A  2A B = 0)
creates the
Steiner inellipse of the triangle ABC, and
TriangleCurve(A, B, C, B C + C A + A B = 0)
creates the Steiner
circumellipse of the triangle ABC.
The input points can be called A, B or C, but in this case you cannot use e.g. x(A) in the equation, because A is interpreted as the barycentric coordinate. 