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Course: Mathematics — Second Preparatory
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Curriculum

Mathematics — Second Preparatory

Text lesson

Applications of Parallelism

Mathematics — Second Preparatory

Applications of Parallelism

Worked examples

Worked examples

Comparison aspectMain ideaKeywords
Example 1
  • Two parallel lines are cut by a transversal. A corresponding angle is (3x + 10)°
  • and the other corresponding angle is 100°. Find x
parallellinestransversalcorresponding
Solution
  • The angles are corresponding
  • so they are equal: 3x + 10 = 100
  • so 3x = 90 and x = 30
anglescorrespondingequal
Example 2Two parallel lines are cut by a transversal. The co-interior angles measure 2x° and 3x°. Find each angleparallellinestransversalinterior
Solution
  • 2x + 3x = 180
  • so 5x = 180 and x = 36. The angles are 72° and 108°. Check: 72 + 108 = 180
anglesCheck
Example 3Two parallel lines are cut by a transversal. The alternate angles measure (x + 20)° and (2x − 50)°. Find the angleparallellinestransversalalternate
Solution
  • The angles are alternate
  • so they are equal: x + 20 = 2x − 50
  • so x = 70. The angle is 70 + 20 = 90°. Check: 2 × 70 − 50 = 90
anglesalternateequalangle
Comparison aspectMain ideaKeywords
Example 4
  • Two parallel lines are cut by a transversal
  • and one of the angles formed measures 65°. Find the measures of all eight angles
parallellinestransversalangles
Solution
  • Corresponding and alternate angles to the 65° angle are equal to it
  • so they are 65°. The co-interior angles are supplementary to it
  • so they are 180 − 65 = 115°. Vertically opposite angles are equal
  • so the eight angles are four angles of 65° and four angles of 115°
Correspondingalternateanglesangle
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