The quadrilateral EFGH is a square.
Because △ AEH △ BFE △ CGF △ DHG (corner)
It is known that the four sides of the quadrilateral EFGH are equal, that is, the quadrilateral is a diamond.
And ∠AEH =∠DHG∠AEH+∠AHE = 90,
So: ∠ dhg+∠ ahe = 90,
So: ∠ ehg = 90.
So: quadrilateral EFGH is a square.
Knowledge and skills 2
It is a square.
Because the diagonal of the quadrilateral ABCD is divided into two,
So: the quadrilateral ABCD is a parallelogram.
Because: AC=BD=(√2)AB.
So: the quadrilateral ABCD is a rectangle.
Because: OA? =OB? =( 1/2)AB,
So: OA? +OB? =AB?
So: △ABO is a right triangle, which is AC⊥BD.
So: AB=BC=CD=DA
So: quadrilateral ABCD is a square.