3.3 Parallel Lines and the Triangle Angle-Sum Theorem

3.3 Parallel Lines and the Triangle Angle-Sum Theorem Chapter 3: Parallel and Perpendicular Lines

3.3 Parallel Lines and the Triangle Angle-Sum Theorem • Theorem 3-7 Triangle Angle-Sum Theorem The angles in a triangle add up to 180°

Triangle Angle-Sum Theorem Find m<1. 1 35° 65°

Triangle Angle-Sum Theorem ΔMNP is a right triangle. <M is a right angle and m<N is 58°. Find m<P.

Using Algebra G Find the values of x, y, and z. 39° 21° Solve for x: 65° x° y° z° F J H Solve for y: Solve for z:

Classifying Triangles Equiangular: All angles congruent Equilateral: All sides congruent 60° 60° 60° Acute Triangle: All angles are less than 90° Right Triangle: One angle is 90° Obtuse Triangle: One angle is greater than 90°

Classifying Angles Isosceles: At least two sides congruent Scalene: No sides congruent

Classifying a Triangle Classify the triangle by its sides and angles.

Using Exterior Angles of Triangles Exterior Angle of a Polygon 1 Exterior Angle m<1 = m<2 + m<3 2 3 Remote Interior Angles Theorem 3-8 Triangle Exterior Angle Theorem The measure of the Exterior Angle is equal to the sum of the two Remote Interior Angles

Using the Exterior Angle Theorem Find each missing angle measure: 113° 40° 1 30° 70° 2 45° 45° 3

Homework • Pg 134 1-28

3.3 Parallel Lines and the Triangle Angle-Sum Theorem