Răspuns:
Explicație pas cu pas:
DG⊥BC ; DG = si ║ EF
⇒BG=AD=6cm ; ⇒ CG=10-6=4 cm
ΔDGC = dreptunghic
DG²=DC²-CG²=5²-4²=25-16=9
DG =√9 =3 cm (DG=EF =3 cm)
Aabcd =(BC+AD)*DG/2 =(10+6)*3/2 =24 cm²
Aabfe =Aefcd =24:2 =12 cm²
Aabfe =BF*FE
12=BF*3
BF=12/3 =4 cm (BF=AE =4 cm ; FC=BC-BF=10-4 =6 cm ;ED =6-4 =2 cm)
Abfe =Aefcd
BF*EF = (FC+ED)*DG/2
4*3 = (6+2)*3/2
12 = 12