Cum PM || AC => ΔPBM~ΔABC => [tex] \frac{MP}{AC}= \frac{MB}{BC}. [/tex]
Cum NM || AB => ΔNMC~ΔABC => [tex] \frac{MN}{AB}= \frac{MC}{BC}. [/tex]
[tex] \frac{MN}{AB}+ \frac{MP}{AC} = \frac{MC}{BC}+ \frac{MB}{BC}= \frac{MC+MB}{BC}= \frac{BC}{BC}=1. [/tex]
*Am avut si eu problema aceasta la un test...anul trecut :).*