MN-linia mijlocie
MN=(AB+AB/2)/2
9=(2AB/2+AB/2)/2
9=(3AB/2)/2
18=3AB/2
36=3AB
AB=12cm -> baza mica, adica CD=AB/2=6cm
Aria = ((AB*CD)*3radical3)/2=(12*6*3radical3)/2=(72*3radical3)/2=36*3radical3=108radical3 cm2
Ducem CE || AD ; CE=AD=3radical3
Aflam latura EB din triunghiul EBC, EB=AB-DC=12-6=6cm
Din teorema lui pitagora ->BC^2=CE^2+EB^2
BC^2=27+36
BC^2=63
BC=radical63
BC=3radical7
Perimetrul este AB+CD+AD+BC=
12+6+3radical3+3radical7=18+3radical3+3radical7 cm
Sper ca te-am ajutat !! :)