Two- Dimensional Figures Lesson 13 Two- Dimensional Figures

Polygons A polygon is a closed, 2-dimensional figure that is made up of line segments that meet at an endpoint. The name of a polygon tells you how many sides, interior angles and vertices it has. The vertex of a polygon is the point at which two sides meet.

Name of the Polygon Number of Sides Number of Interior Angles Number of Vertices Examples Triangle 3 Quadrilateral 4 Pentagon 5 Hexagon 6 Heptagon 7 Octagon 8

Regular and Irregular Regular polygon has all congruent sides and all congruent angles. Irregular polygon is any polygon that is not regular.

Example 1 Classify the polygon. Be sure to mention what type of polygon it is and whether it is regular or irregular. It is irregular. Not all the sides are the same. Notice the tick marks.

Quadrilaterals A trapezoid is a quadrilateral with exactly one pair of parallel sides. A parallelogram is a quadrilateral with opposite sides that are parallel and congruent. A rhombus is a parallelogram with all four sides congruent. A rectangle is a parallelogram with four right angles. A square is a rectangle with all four sides congruent.

Example 2 Mel made this statement: “Every square is also a parallelogram”. Is his statement always true? What are the definitions of a parallelogram or a square? Parallelogram: opposite sides that are parallel and congruent. Square: Rectangle with all sides congruent. Can you draw a square that is a parallelogram? YES! He is correct!

Lets look at page 86 in your Coach book In groups, work on numbers 1-6. Then switch groups to compare answers We will review as a class.

Drumroll….. OPEN ENDED Peter and Jaime are studying two dimensional figures in math class. Peter makes the statement: “Every rhombus is also a square.” Is Peter correct that every rhombus is a square? Explain your answer and sketch at least on example to support your answer. Is Jamie correct that every square is also a rhombus? Explain your answer and sketch at least one example to support your answer.