Kelsey was curious if \triangle ABC△ABCtriangle, A, B, C was congruent to \triangle FED△FEDtriangle, F, E, D, so she tried to map one triangle onto the other using transformations: Kelsey concluded: "It's not possible to map \triangle ABC△ABCtriangle, A, B, C onto \triangle FED△FEDtriangle, F, E, D using a sequence of rigid transformations, so the triangles are not congruent."