10. Which polygon does not always have congruent diagonals? \( \begin{array}{ll}\text { (1) square } & \text { (3) rhombus } \\ \text { (2) rectangle } & \text { (4) isosceles trapezoid }\end{array} \)

An isosceles trapezoid typically has one pair of congruent sides and one pair of congruent angles, which helps in establishing a certain symmetry. However, the diagonals of an isosceles trapezoid do not always have the same length unless they are specifically set to do so, making it the only option here where diagonals aren’t always congruent. In contrast, both rectangles and squares have diagonals that are always equal, as do rhombuses, due to their unique properties. This makes those shapes reliable when it comes to diagonal congruence—a fun fact if you’re sketching polygons or calculating their properties!