Example: When solving for diagonal length in a rectangle, the Pythagorean theorem is applied: BD² = AC² + BC².

Highlight: The page demonstrates how to use algebraic expressions to solve for unknown sides and angles in quadrilaterals.

Definition: In a rhombus, diagonals are perpendicular to each other and bisect the angles of the rhombus.

Vocabulary: Congruent means equal in size and shape, a key concept when working with parallel sides and angles in quadrilaterals.

Definition: A polygon's interior angle sum can be calculated using the formula: $n-2$ × 180°, where n is the number of sides.

Example: For a 27-sided polygon $27-gon$, the interior angle sum is $27-2$ × 180° = 4500°.

Vocabulary: A parallelogram is a quadrilateral with opposite sides parallel and equal.

Highlight: Regular polygons have all sides equal and all interior angles equal, making them particularly useful in geometric calculations.