m12.
AB=6
BE_I_CD
m(∡BCD)=45° triunghiul BCE dreptunghic isoscel ⇒EC=BE=8 cm
ducem AF_I_DC ⇒ DF=AF=8 cm
DC=6+2*8=22 cm
16.
ducem BE_I_ CD m(∡CBE)=120°-90°=30°
Teorema unghiului de 30°⇒EC=BC/2=8/2=4 cm
AB=DE=4
CD=DE+EC=4+4=8 cm
BE=√(8²-4²)=√(64-16)=√48=4√3 cm
BD=√[4²+(4√3)²]=√(16+48)=√64=8 cm
