设边长为A,由面积 A^2/2=1,得边长 A^2=2,A=2^(1/2)
周长 L = 2A + 2^(1/2)A = 2*2^(1/2) + 2^(1/2)2^(1/2)
=2*2^(1/2)+2 =4.83