Răspuns :
[tex]\it Not\breve am:\ AM=x,\ \ MN=y,\ \ AN=z.\\ \\ Rezult\breve a:\ AB=2x,\ \ BC=2y,\ \ AC=2z.\\ \\ \mathcal{P}_{ABC}=AB+BC+AC=2x+2y+2z=2(x+y+z)=2\cdot\mathcal{P}_{AMN} \\ \\ Deci,\ \mathcal{P}_{ABC}=2\cdot \mathcal{P}_{AMN} \Rightarrow \mathcal{P}_{AMN}=\dfrac{\mathcal{P}_{ABC}}{2}[/tex]