One angle is exactly 90°. The side opposite this angle is the hypotenuse (the longest side). Obtuse: One angle is greater than 90°. Key Triangle Theorems
A parallelogram with four right angles (90°). Its diagonals are equal in length. properties of triangles and quadrilaterals
A quadrilateral is a polygon with four sides and four vertices. The sum of the interior angles of a quadrilateral is always 360 degrees. One angle is exactly 90°
A has all interior angles < 180° and diagonals inside. 180° and diagonals inside.