Quadrilaterals: types and properties
Plane geometry · Mathematics
Study notes
Q: A quadrilateral has angles 80°, 100°, 90°. Find the fourth. Name a quadrilateral with both pairs of opposite sides parallel. Fourth: 360° - 80° - 100° - 90° = 90°. Both pairs parallel: PARALLELOGRAM! Hierarchy: square ⊂ rectangle ⊂ parallelogram ⊂ quadrilateral!