# Lesson 13 Two Dimensional Figures Polygons A polygon

- Slides: 9

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 Triangle 3 3 3 Quadrilateral 4 4 4 Pentagon 5 5 5 Hexagon 6 6 6 Heptagon 7 7 7 Octagon 8 8 8 Examples

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.

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