4.1 Triangle Sum Theorem & Exterior Angle Theorem

1. 4.1 Triangle Sum Theorem&Exterior Angle Theorem

2. A triangle is a polygon with three sides. • A triangle with vertices A, B, and C is called “triangle ABC” or “∆ABC.” Classifying Triangles by Sides • A scalene triangle is a triangle with no congruent sides. • An isosceles triangle is a triangle with at least two congruent sides.

3. An equilateral triangle is a triangle with three congruent sides. Classifying Triangles by Angles • An acute triangle is a triangle with three acute angles. • A right triangle is a triangle with one right angle. • An obtuse triangle is a triangle with one obtuse angle.

4. 1 3 2 Triangle Sum Theorem The sum of the angle measures in a triangle equal 180° m<1 + m<2 + m<3 = 180°

5. exterior angle remote interior angles 2 1 3 4 Exterior Angle Theorem(your new best friend) The measure of an exterior angle in a triangle is the sum of the measures of the 2 remoteinterior angles m<4 = m<1 + m<2

6. 30x find all the angle measures Do you hear the sirens????? 40x 10x2 an example with numbers find x & y 82° x = 68° y = 112° 30° x y 80°, 60°, 40°

8. Ex.6: The tiled staircase shown forms a right triangle. The measure of one acute angle in the triangle is twice the measure of the other. Find the measure of each acute angle.

9. Ex.9: Find the measures of the acute angles of the right triangle in the diagram shown.

10. Desk Work Please get, or have someone get for you; marker eraser

11. Classwork