a) ΔAMN: MF=FN si MF⊥AB → ΔAMN - isoscel → AM = AN; ΔPAM: AE⊥MP si ME=EP → ΔMAP = isoscel → AM = AP. Dar AM = AN → AP = AN → ΔPAN - isoscel.
b) ΔPCM = ΔNMB: MC=MB; MCP = MBN = 90°; MN = MP (deoarece MF = ME din congruenta triunghiurilor MEC si MFB) → BN = CP.
AE=AF si CE=FB → AE/AC = AF/AB → EF ║BC