Duc inaltimea BD si in trg dreptunghic ABD , aplic teorema unghiului de 30 de grade pt ca m(ABD)=30 grade
rezulta ca AD=AB/2=6/2=3 si CD=10-3=7
aplic T Pitagora si aflu BD^2
BD^2=AB^2-AD^2=36-9=27
in trg BDC aplic inca o data T Pitagora
BC^2=BD^2+CD^2=27+49=76
BC=V76=V4*19=2V19
