1. GEOMETRY What lies behind us and what lies before us are tiny matters compared to what lies within us. Ralph Waldo Emerson Today: – 11.1 Instruction – Practice

2. 11.1 Angle Measures in Polygons Objectives: Find measure interior angles of polygons Find measure exterior angles of polygons Vocabulary: interior angles, exterior angles

3. polygon # of sides # of triangles Sum of interior angles triangle quadrilateral pentagon hexagon heptagon octagon decagon 20-gon n-gon

4. polygon # of sides # of triangles Sum of interior angles triangle311x180=180 quadrilateral pentagon hexagon heptagon octagon decagon 20-gon n-gon

5. polygon # of sides # of triangles Sum of interior angles triangle311x180=180 quadrilateral 42 2x180=360 pentagon hexagon heptagon octagon decagon 20-gon n-gon

6. polygon # of sides # of triangles Sum of interior angles triangle311x180=180 quadrilateral 42 2x180=360 pentagon 53 3x180=540 hexagon 64 4x180=720 heptagon 75 5x180=900 octagon 86 6x180=1080 decagon 108 8x180=1440 20-gon 2018 18x180=3240 n-gon

7. polygon # of sides # of triangles Sum of interior angles triangle311x180=180 quadrilateral 42 2x180=360 pentagon 53 3x180=540 hexagon 64 4x180=720 heptagon 75 5x180=900 octagon 86 6x180=1080 decagon 108 8x180=1440 20-gon 2018 18x180=3240 n-gon nn - 2 (n-2)x180

8. Find the sum of the interior angles of a regular nonagon. 1260° What is the measure of each interior angle? 140°

9. Find the measure of each interior angle of a regular quadrilateral. 90° Find the measure of each exterior angle of a equilateral triangle. 120° Find exterior angle of the same regular quadrilateral. 90°

10. The sum of the measures of the exterior angles of a convex polygon, one angle at each vertex is ___________. 360 What is the measure of an exterior angle for regular hexagon? 60°

11. A regular polygon has exterior angles of 18°, how many sides in this polygon. 20 A regular polygon has interior angles of 150°, how many sides in this polygon. 12

12. x x x 3x 2x x = 67.5 º x + 20 x x 2x x = 85 º

13. Find y. 60° y y 2y

14. 11.1 Angle Measures in Polygons What lies behind us and what lies before us are tiny matters compared to what lies within us. Ralph Waldo Emerson Assignment: p 708 #1-7 odd and p 712 #1, 2, 12 – 16