alternate interior angles, corresponding angles, transversal
TEKS 8(1)(F), 8(8)(D)
Example Finding Angle Measures Using Parallel Lines
In the diagram, a||b and c||d. If m∠1 = 60°, what is m∠6?
Method 1 ∠2 and ∠1 are corresponding angles formed by parallel lines a and b and transversal c, so they are congruent. Congruent angles have equal measures, so m∠2 = 60°.
∠4 and ∠2 are corresponding angles formed by parallel lines c and d and transversal b, so they are congruent. Congruent angles have equal measures, so m∠4 = 60°.
∠4 and ∠6 form a straight angle, so they are supplementary angles.
table with 3 rows and 1 column , row1 column 1 , m angle 4 plus m angle 6 equals 180 degrees , row2 column 1 , 60 degrees plus m angle 6 equals 180 degrees , row3 column 1 , m angle 6 equals 120 degrees , end table