7.
aria=684=BC x AD/2, AD⊥BC
BC=2 x 684/AD=1368/36
BC=38
9.
daca BM=MN=NC rezulta ca triunghiurile ABM,AMN,ANC sunt echivalente adica au arii egale lucru usor de aratat ( au baze egale si aceiasi inaltime)
aria ABC At
At=BC x H/2=(BM+MN+NC) x H/2 = 18 cm2, H e inaltimea din varful A
BM x H/2 = MN x H/2= NC x H/2 = 18/3=6
aria AMN=6 cm2
aria AMC= 2 x aria AMN =12 cm2
