3. A quadrilateral is a polygon with FOUR sides. Q S R P It is named by its VERTICES in a clockwise position. *The figure above is named PQRS, QRSP, RSPQ, or SPQR. 2 31 4 REMEMBER :The order of the vertices is important !

4. TERMS : D C B A In quadrilateral ABCD, the vertices are A, B, C and D. Vertices A and B, B and C, C and D, D and A are consecutive vertices. Vertices A and C, B and D, are opposite vertices.

5. A B D C Two sides with a common vertex, like AB and BC, are consecutive sides. AB, and DC, AD and BC, on the other hand are opposite sides.

6. ` D BA C Two angles with a common side, like <A and <D, are consecutive angles. <A and <C, <B and <D, on the other hand are opposite angles.

7. A B C D Segments joining opposite vertices like AC and BD are called diagonals of the quadrilateral.

8. KINDS of QUADRILATERALS : M N O P Q R S T CONVEX NONCONVEX Diagonals of quadrilateral intersect. Diagonals of quadrilateral do not intersect

9. TYPES of QUADRILATERALS : Trapezoid Parallelogram Rectangle Rhombus Square Quadrilateral

10. TRAPEZOID A trapezoid is a quadrilateral with exactly a pair of parallel sides. base angles base leg *If the legs are congruent, trapezoid is an isosceles. *If a quadrilateral has no parallel sides, it is called a trapezium.

11. PARALLELOGRAM A parallelogram is a quadrilateral with two pairs of congruent and parallel sides.

12. RECTANGLE A rectangle is a parallelogram with four right angles.

13. RHOMBUS A rhombus is a parallelogram with four congruent sides.

14. SQUARE A square is a parallelogram with four congruent sides and four congruent angles.

15. Parallelogram Rhombus Rectangle Square REMEMBER ! always sometimes

16. MARIVIC M. MARQUINEZ II – B BSE Mathematics