are o cateta =ipotenuza/2=20/2=10cm (teorema unghiuluide 30° in triunghiul dreptunghic)
si are cealalta cateta =Pitagora= √(ipotenuza ²- cateta²)=√(20²-10²)-
√(400-100)=√300=√(100*3)=√100 *√3=10√3
aria tr.dr=cateta1*cateta 2/2=(10*10√3)/2=(100√3)/2=50√3b cm²
as explicit as that!!
