1. Classifying Triangles Classifying by Angles: Acute - 3 acute angles Obtuse - 1 obtuse angle Right - 1 right angle Equiangular – An acute triangle with 3 congruent angles

2. Classifying Triangles Classifying by Sides: Scalene - No sides congruent. Isosceles - At least 2 sides congruent. Equilateral - All sides congruent.

3. Example 1-1b ARCHITECTURE The frame of this window design is made up of many triangles. Classify  ABC,  ACD, and  ADE as acute, equiangular, obtuse, or right. Answer:  ABC is acute.  ACD is obtuse.  ADE is right.

4. Example 1-2c Identify the indicated triangles in the figure. a. isosceles triangles b. scalene triangles Answer:  ABC,  EBC,  DEB,  DCE,  ADC,  ABD Answer:  ADE,  ABE

5. Example 1-3c Answer: ALGEBRA Find d and the measure of each side of equilateral triangle if and

6. Example 1-4c Find the measures of the sides of  ABC. Classify the triangle by sides. Answer: ; since all 3 sides have different lengths,  ABC is scalene.