Not always X All sides are congruent. (Only for rectangles that are also rhombus = a square!)
Not always X The diagonals of a rectangle are perpendicular to each other. (Counterexample: draw a really long rectangle with a tiny, tiny width...the x made by the diagonals is clearly not perpendicular!)
True☆ The opposite sides are parallel. (Bc rectangles are parallelograms, part of the definition)
True☆All angles are congruent. (All four angles are right angles--part of the definition)
The contributors to the proof are listed in the left column. They consist of a congruent Side, a congruent Angle, and a congruent Side. The SAS Postulate is an appropriate choice.
