АВ=ВС=АС=1 SA=SB=SC=1 АО=(2/3) AD; D- cередина BC; AD^2=AB^2-BD^2=1^2-(1/2)^2=1-(1/4)=3/4 AD=sqrt(3)/2 AO=sqrt(3)/3 SO^2=AS^2A-AO^2=1-(3/9)=2/3 SO=sqrt(2/3)