Răspuns :
A=(AB.BC.sin B)/2=4.5.√3/2.1/2=
5√3
sin120=sin(60+60)=sin60cos60+sin60cos60=2*1/2*√3/2=√3/2
5√3
sin120=sin(60+60)=sin60cos60+sin60cos60=2*1/2*√3/2=√3/2