Notam / = impartire ; fractie
HG || EF => Cu teorema fundamentala a asemanarii avem : ΔDHG ≡ ΔDEF
=> Avem laturi proportionale :
DH/DE = HG/EF = DG / DF
DH/9+DH = 4/10 = DG / 6+DG
Luam primele doua fractii : DH/DH+9 = 4/10 => 4(DH+9) = 10 DH
4DH + 36 = 10 DH
(...) DH = 6
Luam ultimele doua fractii DG / DG+6 = 4/10 => 4(DG+6) = 10 DG
4DG + 24 = 10 DG
(...) DG = 4
Aflam PΔDHG = DH + HG + DG = 6 + 4 + 4 = 14