>>6
∠COD=∠BOA=∠AOG=∠GOF=π/4
∠DOC=∠EOD=∠FOD=π/3
とすると、
七角形の面積S=4△COD+3△DOC
七角形の周長L=4BC+3CD
S=4(1/2)(1/√2)+3(1/2){(√3)/2}
=√2+(3√3)/4
BC=√[{(1-(1/√2)}^2+(1/√2)^2]
=√(2-√2)
L=4√(2-√2)+3