daca unghiurile de la baza au 45*
inseamna ca daca ducem inaltimea se formeaza un triunghi isoscel
AE||DC
ΔDAE are DE=AE=(16-4):2=6 cm
deci inaltimea e 6 cm
A=(B+b).h/2=(16+4).6/2=60 cm²
b)A(ΔBOC)/A(ΔABCD)
A(ABCD)=A(DOC)+A(AOB)+2A(BOC)
A(BOC)=A(AOD)
OF_|_DC
ΔCFO≈ΔCEA
CF/CE=OF/AE
8/10=OF/6
OF=48/10
OG_|_AB
OG=6-48/10=12/10
atunci
16/2.48/10+4/2.12/10+2A(BOC)=60
calculand
A(BOC)=192/20=96/10atunci raportul este
96/10:60=96/600=16/100=4/25
