1. Section 1.8

2. Polygon – A closed figure that 1. the sides have common endpoints that are not collinear 2. Each side intersects exactly two other side at their endpoints

3. Is this a polygon? 1.3. 2.4.

4. Concave – some/any of the sides when extended pass through the inside Convex - none of the sides when extended pass through the middle

5. Is this a concave or convex polygon? 1.2. 3.4.

6. Polygons NameNumber of Sides Triangle3 Quadrilateral4 Pentagon5 Hexagon6 Heptagon7

7. Octagon8 Nonagon9 Decagon10 Dodecagon12 n-gonn

8. Regular Polygon – convex polygon with all sides and all angles congruent

9. Perimeter Perimeter – the sum of the lengths of a polygons sides. Example: P = 32 5x 2x 6x 3x

10. Try: Find the perimeter 1. 2. P = 60 18 2x 12 3x 5 5 5 5 5 5

11. Common Perimeter Formulas Square = 4(length) Rectangle = 2l + 2w Regular polygon = (number of sides)(length of sides)

12. If you are given points… 1.Use the distance formula to find the length of sides given the coordinates. d = 2. Add up all the lengths to find the perimeter

13. Example: Find the perimeter (0, 0) (3, 5) (7, 0)

14. Try: Find the perimeter (-2, 1) (-2, 7) (6, 1) (6, 7)

15. Class Work Worksheet!