<2 are 60 grd pt ca CDE trg echilateral
< EBA=90-15=75grd
AE=EB pt ca trg AED si BEC sunt cong : AD=BC, CE=DE si <BCE=<ADE
trg EBA isoscel cu <EBA=<EAB=75 grd
in trg EBA <4=180-(75+75)=30 grd
<6 =90- 75=15 grd
<5=180-(90+<6)=180-105=75 grd
unghiul suplementar lui 3 are masura 180-(90+<1)=180-(90+15)=75 grd
rezulta <3=180-75=105 grd