mas∡ D=0,(6)mas ∡A=6/9mas ∡A=2/3 mas ∡A
dar ∡A si ∡D suplementare , ABCD trapez
mas A+2/3 mas A=180°
5/3 mas∡A=180°
mas∡ A=180°*3/5=108°
mas ∡D=180°-106°=72°
AB=AD , ABD isoscel baza BD
mas ∡(ABD)=(180°-108°)/2=36°=mas ∡(BDC) -alterne interne
fie {O}=AC∩BD
ABCD trapez isoscel, DOC triunghi isoscel baza DC
⇒mas ∡(OCD)=mas ∡(ODC)=36°
DC=35-8-8-8=11 cm
Fie AE⊥DC, E∈AC
AC²=AE²+ EC²
DE = (11-8)/2 =3/2⇒EC=11-3/2=19/2
AE²=8²-(3/2)²=64-9/4
eci AC²=64-9/4 +(19/2)²=64-9/4+361/4=(256-9+361)/4=608/4=152
Ac =√152=2√38
