1. 1Geometry Lesson: Polygons, Triangles Aim: Do Now: 2) Which of the following shapes are polygons? e) a) b) c) d) f) What are polygons? How do we classify triangles? A D P C B

2. 2Geometry Lesson: Polygons, Triangles Def: Polygons A polygon is a closed figure that is the union of line segments that intersect only at their endpoints. Def: Regular Polygons: All angles and all sides of a regular polygon are equal in measure.

3. 3Geometry Lesson: Polygons, Triangles Triangles: P Q R A triangle is a polygon with exactly three sides. Sides of Angles of

4. 4Geometry Lesson: Polygons, Triangles “Included” Sides and Angles of Triangles P Q R Two angles that share a side “include” the side. Two sides “include” the angle between them.

5. 5Geometry Lesson: Polygons, Triangles “Opposite” Sides and Angles of Triangles P Q R Each angle of a triangle has an opposite side, and vice versa.

6. 6Geometry Lesson: Polygons, Triangles Def: An triangle has at least two congruent sides. Def: An triangle has three congruent sides. Classifying Triangles by Sides: Equilateral Isosceles Def: A triangle has no congruent sides. Scalene

7. 7Geometry Lesson: Polygons, Triangles Isosceles Triangle: 1) The 2 congruent sides are known as. 2) The non-congruent side is the. 3) Angles opposite the legs are the. C A B 4) The angle included by the legs is the. base Base. base angle Base Angles. vertex Vertex Angle. leg Legs. R P Q Base Legs Vertex Angle Base Angles A B C D E ABCDE is a regular pentagon Base Legs Vertex Angle Base Angles What type of triangle is ?

8. 8Geometry Lesson: Polygons, Triangles Def: A triangle having three congruent angles is an triangle. Classifying Triangles According to Angles: Def: A triangle having three acute angles is an triangle. Acute Triangle. Equiangular Triangle. Def: A triangle having a right angle is a triangle Right Triangle. Def: A triangle having an obtuse angle is an triangle Obtuse Triangle.

9. 9Geometry Lesson: Polygons, Triangles Right Triangles: 1) The side opposite the right angle is the. 3) The longest side is the. Hypotenuse. 2) The sides opposite the acute angles are.Legs. leg Hypotenuse. hypotenuse 4) Pythagorean Theorem: a b c Example: A triangle has sides measuring 9, 12, and 14 cm. Show that this triangle is not a right triangle.