1. Triangles Objective: Learn to name and classify triangles.

2. Triangles are polygons with 3 sides. They can be classified by the number of congruent (equal) sides they have. There are 3 types of triangles:  Equilateral Triangles: are triangles that have 3 congruent (equal) sides.  Isosceles Triangles: are triangles that have 2 congruent (equal) sides.  Scalene Triangles: Triangles that have no congruent side.

3. Triangle Cartoon:

4. You can also classify triangles by their angle measures.  Acute Triangles: Triangles in which all angles are acute. All angles are less than 90 degrees.  Right Triangles: is when a triangle has one right angle.  ObtuseTriangles: when the triangle has one obtuse angle.

5. All 3 angles in a triangle add up to 180 0. Steps: 1.Draw a triangle with a ruler. 2.Cut the triangle. 3.Cut the 3 corners of your triangle. 4.Join the 3 angles (corners). 5. What do they form??? ___________________ Rule: The sum of all angles in a triangle add up to 180 degrees.

6. Examples:  Find the measure of the unknown angle. If m<1 = 40, and the m<2 is 70, what is m<3 ?  Find the measure of the unknown angle. If the m<1= 35 and the m<J is 115, what is the measurement in <K?

7. Homework: In exercises 1-9: Find the missing angle and write if the triangles are acute, right, or obtuse. In exercises 10-15: Write if each angle is acute, right, or obtuse AND if they are equilateral, isosceles, or scalene.