It is proved that the intersection of EF, GH and BD is p and q respectively.
∫EH//BD//FG
∴ △AEH, △ABD, △CFG and △CBD are isosceles right triangles.
△AEH?△CFG
AE=CF
AB = BC
∴? △BEF is an isosceles right triangle.
EPQH is rectangular.
EH=PQ? EP=BP? Headquarters =DQ
EP+EH+HQ=BD
In the same way; In a similar way
FP+FG+GQ=BD
Circumference of quadrilateral EFGH = 2BD
According to Pythagorean theorem
BD=√2AB=√2* 1/4 square ABCD perimeter = √2a.
Circumference of quadrilateral EFGH = 2√2a