1. Warm Up 98 What is the measure of an acute angle? ____________________ What is the measure of a right angle? ____________________ What is the measure of an obtuse angle? _____________________

2. Equipment needed for constructions Before you begin make sure you have the following equipment: A protractor A ruler A sharp pencil

3. A protractor is used to measure angles Place the center of the protractor on the vertex of the angle so that the horizontal line lies on one of the rays of the angle. The other ray will fall on of the numbers of the protractor.

4. Let’s Practice Using our Protractors

5. Triangles Facts 1.The sum of the measures of the interior angles of a triangle equals 180°. 2.The sum of the two smaller sides of a triangle must be greater than the longest side. Proof Tear a triangle in 3 pieces so that the angles are separated. Reassemble the triangle so that the vertices meet at the same point. A straight angle is formed. A straight angle measures 180°.

6. Triangles can be classified by the measures of their angles and lengths of their sides. Types of angles: 1.Acute 2.Obtuse 3.Right Side Lengths 1.Scalene 2.Equilateral 3.Isosceles Scalene – no equal side lengths Equilateral – 3 equal (congruent) side lengths and three angles equal in measure Isosceles – 2 equal (congruent) sides and two congruent angles

7. Classify triangles by their angles & side lengths acute equilateral – all angles are acute all sides are congruent obtuse scalene – largest angle is obtuse ; no congruent sides right isosceles – has one right angle ; two congruent sides right scalene – there is one right angle and no congruent sides