Parallelograms or isosceles trapezium.
No. An isosceles trapezium (isosceles triangle with its apex removed) would have congruent diagonals but it is not a parallelogram.
All quadrilaterals have 2 diagonals
The diagonals of a rectangle are always congruent. This means that both diagonals have the same length, which is a property unique to rectangles and other types of quadrilaterals like squares. This congruence arises from the fact that rectangles have opposite sides that are equal in length and all angles that are right angles.
No. A small pentagon will have smaller diagonals than a large pentagon! However, all the diagonals of a regular pentagon will be congruent.
All quadrilaterals (four sided shapes) have 2 diagonals.
square
Not generally.
Rectangles
No. An isosceles trapezium (isosceles triangle with its apex removed) would have congruent diagonals but it is not a parallelogram.
Most quadrilaterals do not.
A square and a rectangle have diagonals of the same lengths.
Most quadrilaterals will not have congruent diagonals: rectangles (incl squares) and isosceles trapezium are the exception.
rectangle and parallelogram
rectangle and parallelogram
there is nothing listed
A square
square, rectangle and an isosceles trapezoid.