which of the following are necessary when proving that the diagonals of a rectangle are congruent check all that apply

 When proving that the diagonals of a rectangle are congruent, you need to verify a few geometric properties according to the definitions and theorems of Euclidean geometry. Specifically, the following are necessary:

1. Definition of a rectangle: You need to recognize that a rectangle is a quadrilateral with four right angles. 2. Congruent Angles: Since a rectangle has four right angles, it is easily established that opposite angles are congruent (all are 90 degrees). 3. Definition of congruency: Understanding what it means for two segments to be congruent, which is having the same length. 4. Properties of parallelograms: Since a rectangle is a type of parallelogram, properties that state opposite sides are congruent can be used as part of the proof. 5. Understanding of diagonal: Knowing what a diagonal of a polygon is, which in this case, is a line segment connecting two opposite vertices of the rectangle.

Additional methods or theorems may be used based on the proof technique, but generally, these are the fundamental aspects to consider for such a proof.