Children with expressive language disorder have difficulty conveying or expressing information in speech, writing, sign language or gesture. (For preschool children, the difficulty expressing themselves in writing is not evident, as they have not started formal education.)
A rectangle is defined as a parallelogram (a quadrilateral with two sets of parallel sides) with the non-parallel sides joining perpendicularly (at 90Â°). A square is a rectangle with the additional constraint the all four sides be of equal length.
A rectangle is a parallelogram with 4 right angles. Now, since a rectangle is a parallelogram, its opposite sides must be congruent and it must satisfy all other properties of parallelograms. In a rectangle, all angles are 90Â°. The diagonals of a rectangle are congruent. It's easy to prove that the diagonals of a rectangle with the Pythagorean theorem.