A_(1)C_(1)=2r=2sqrt(7)
A_(1)C_(1)- диагональ квадрата А_(1)B_(1)C_(1)D_(1)
A_(1)B_(1)=AC*sin45 ° =2sqrt(7)*sqrt(2)/2=[b]sqrt(14)[/b]
АВ=2ОК=2sqrt(7)
S_(A_(1)B_(1)C_(1)D_(1)):S_(ABCD)=(A_(1)B_(1))^2:(AB)^2=
=(sqrt(14))^2:(2sqrt(7))^2=14:(4*7)=[b]1:2[/b]