Yes.
Yes the diagonals of a square are always congruent. Their length is a*root 2 where a is the side of the square.
square
Yes.
Square.
It is a square.
square
square
A square
square
Regular polygons. A square and rectangle will have congruent (equal length) diagonals.
No. If the diagonals of a parallelogram are congruent then it must be a rectangle (or square).
square and rectangle