va rogggg repede dau coroana

Răspuns:
a)∆ABC≈∆AMN
raportul de asemănare fiind 2/3
AM/AB=AN/AC=MN/BC=/2/3
AM=2×18/3=12cm
AN=2×21/3=14cm
MN=2×15/3=10cm
P∆AMN=12+14+10=36cm
b)P∆ABC=(36/2)×3=108/2=54cm
deoarece P∆ABC/P∆AMN=2/3