A line can be specified in trilinear coordinates by parameters (l, m, n) such that the trilinear coordinates α:β:γ obey l α + m β + n γ = 0. The trilinear line at infinity of a triangle with side lengths a, b, and c is a α + b β + c γ = 0. The line passing through points α_1 :β_1 :γ_1 and α_2 :β_2 :γ_2 is given by l | = | β_1 γ_2 - γ_1 β_2 m | = | γ_1 α_2 - α_1 γ_2 n | = | α_1 β_2 - β_1 α_2.

central line | line | line-line angle | trilinear coordinates