The Steiner-Lehmus theorem and "triangles with congruent medians are isosceles" hold in weak geometries

Victor Pambuccian, Horst Struve, Rolf Struve

We prove that (i) a generalization of the Steiner-Lehmus theorem due to A. Henderson holds in Bachmann's standard ordered metric planes, (ii) that a variant of Steiner-Lehmus holds…