Lesson 8 Finding Missing Angles in Parallel Lines

Lesson 8: Finding Missing Angles in Parallel Lines that have been Intersected by a Transversal Unit 4 Lines, Angles, Triangles, and Quadrilaterals

Review: • Corresponding Angles: a pair of angles the same side of a transversal crossing a pair of parallel lines a=e b=f c=g d=h 4 pairs of angles: a and e b and f c and g d and h

Review • Alternate Angles: a pair of equal angels found between a pair of parallel lines and on opposite sides of a transversal c and f are one pair. e and d are another pair. c=f e=d

Review • Interior Angles: a pair of supplementary angles formed between a pair of parallel lines and on the same side of a transversal. These are also known as co-interior angles

How to Find Missing Angles: Example: D G A H B 131 o C F E Find <EHB, <FHG, and <EHG.

Finding Missing Angles D G A H B 131 o C F E Solution: 1) Identify the angle relationships: Corresponding - <CGH and <EHB Alternate - <CGH and <FHG Interior - <CGH and <EHG

Finding Missing Angles 2) Calculate: <CGH = <EHB 131 o = 131 o therefore, <EHB is 131 o <CGH = <FHG 131 o = 131 o therefore, <FHG is 131 o <CGH + <EHG = 180 o 131 o + <EHG = 180 o - 131 o therefore, <EHG is 49 o

Finding Missing Angles 3) State your answer: D G A H B 131 o C F E <EHB is 131 o, <FHG is 131 o, and <EHG is 49 o

Practice • Complete the following questions in your notebook: – Textbook page 438 #1, 4 -6, 9, 11, 17