NM II AC ⇒ Δ MBN ≈ ΔCBA
MB / BC = BN / AB = MN / AC
din rapoarte fie : MB/BC = BN/AB schimbam locurile
AB/ BC = BN /MB
MP II AB ⇒ Δ CMP ≈ Δ CBA
CM / BC = CP /AC = MP/ AB
fie CM /BC = MP /AB
AB / BC = MP / CM
⇒ BN / MB = MP / CM schimbam termenii
BN MB Δ BNM
---------- = ---------- ⇒ asemenea
MP CM Δ MPC