The three planes determined by the edges of a trihedron and the internal bisectors of the respectively opposite faces are coaxal, and the common line of these planes is called the centroidal line.
Centroidal Line
See also
TrihedronExplore with Wolfram|Alpha
References
Altshiller-Court, N. "Centroidal Lines." §2.5 in Modern Pure Solid Geometry. New York: Chelsea, pp. 40-41, 1979.Referenced on Wolfram|Alpha
Centroidal LineCite this as:
Weisstein, Eric W. "Centroidal Line." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/CentroidalLine.html