AC=m*sqrt(2)
АМ^2=AB^2+BM^2=m^2+(m/2)^2=m^2+(m^2/4)=5m^2/4
AM=m*sqrt(5)/2
СM=AM=m*sqrt(5)/2
P_(сечения)=АМ+СМ+АС=m*sqrt(5)/2+m*sqrt(5)/2+m*sqrt(2)=[b]m*(sqrt(5)+sqrt(2))
[/b]
S_(сечения)=(1/2)(AC*MO)
О- точка пересечения АС и BD.
MO^2=BO^2+BM^2=((1/2)m*sqrt(2))^2+(m/2)^2=3m^2/4
MO=(1/2)*m*sqrt(3)
S_(сечения)=(1/2)(m*sqrt(2)*(1/2)*m*sqrt(3))=[b](1/4)m^2*sqrt(6)[/b]