E,cam,lunga,rezolvarea,sper,s-o,intelegi...
Am,construit,triunghiul,ABC,cu,baza,BC
Am,coborat,inaltimea,AD,pe,baza,BC,care,este,20cm(ipoteza)
Se,formeaza,doua,triunghiuri,dreptunghice,ADB,si,ADC.
In,Δdr.ADB,avem,AD=AB/2(teorema,∡30°)=>AB=40
Cu,t.Pit.aflam,si,cealalta,cateta,BD²=AB²-AD²;BD²=1600-400;BD²=1200
BD=20√3
In,Δdr.ADC,avem,m(∡C)=180°-105°-30°=45°,m(∡D)=90°=>m(∡DAC)=45°
=>ΔADC,dreptunghic,isoscel=>AD=DC=20
=>Baza,ΔABC=20√3+20=20(√3+1)
Inaltimea,o,avem,din,ipoteza
=>Aria=20(√3+1)x20/2=200(√3+1)cm²
