1. 3.4: THE POLYGON ANGLE-SUM THEOREM OBJECTIVE: STUDENTS WILL BE ABLE TO… TO CLASSIFY POLYGONS, AND TO FIND THE SUMS OF INTERIOR AND EXTERIOR ANGLES OF POLYGONS

2. HELLO!!! It’s going to be a good day

3. POLYGON: CLOSED PLANE FIGURE AT LEAST 3 SIDES THAT ARE SEGMENTS SIDES INTERSECT ONLY AT ENDPOINTS ADJACENT SIDES ARE NOT COLLINEAR POLYGONSNOT POLYGONS

4. TO NAME A POLYGON: START AT ANY VERTEX LIST VERTICES CONSECUTIVELY NAME THE POLYGON. NAME THE SIDES AND ANGLES. E D C B A

5. COMMON POLYGONS: SIDESNAME 3Triangle 4Quadrilateral 5Pentagon 6Hexagon 8Octagon 9Nonagon 10Decagon 12Dodecagon nn- gon

6. DIAGONAL OF A POLYGON A SEGMENT IN A POLYGON DRAWN FROM A VERTEX TO A NONADJACENT VERTEX

7. CONVEX VS. CONCAVE CONVEX POLYGON NO DIAGONAL WITH POINTS OUTSIDE POLYGON CONCAVE POLYGON AT LEAST ONE DIAGONAL OUTSIDE POLYGON

8. POLYGON-ANGLE-SUM THEOREM THE SUM OF THE MEASURES OF ANGLES IN AN N-GON : (N-2)180 EXAMPLE: FIND THE SUM OF THE MEASURES OF A 15-GON.

9. FINDING MISSING ANGLE MEASURES FIGURE OUT WHAT THE SUM OF THE INTERIOR ANGLES SHOULD BE ADD UP EXPRESSIONS AND SET THEM EQUAL TO THE SUM FROM PART ONE. EXAMPLE: FIND Y. 120° 85° y° 53°

10. Example: 1.The sum of the measures of a given polygon is 720. How many sides are in the polygon? 2.Pentagon ABCDE has 5 congruent angles. Find the measure of each angle.

11. POLYGON-EXTERIOR-ANGLE SUM THEOREM THE SUM OF THE MEASURES OF EXTERIOR ANGLES OF A POLYGON IS ALWAYS 360 ⁰. EXAMPLE: WHAT IS THE SUM OF EXTERIOR ANGLES FOR A 500-GON?

12. EQUILATERAL POLYGON: All sides EQUIANGULAR POLYGON: All angles REGULAR POLYGON: equilateral and equiangular If you have a REGULAR POLYGON, to find: ONE Interior Measure: ONE Exterior measure:

13. Examples: 1.The sum of the measures of angles of a polygon with n sides is 1980. Find n, the number of sides. 2. Find the measures of one interior angle and one exterior angle of a REGULAR hexagon. 3. The measure of an exterior angle of a regular polygon is 30 ⁰. What is the measure of an interior angle? How many sides are there?

14. TYPE 2: WRITE AND ANSWER THE FOLLOWING ON A SEPARATE PIECE OF PAPER. (2 POINTS EACH QUESTION) 1.FIND THE SUM OF THE INTERIOR AND EXTERIOR ANGLES OF AN OCTAGON. 2.FIND THE MEASURE OF ONE INTERIOR ANGLE AND ONE EXTERIOR ANGLE OF A REGULAR 15-GON. 3.THE SUM OF THE INTERIOR ANGLES OF A POLYGON IS 4680°. FIND THE NUMBER OF SIDES.