Lesson 2: Transversals - Supplementary and Complementary Angles

   Constructing Knowledge

Supplementary and complementary angles can also be used to assist in calculating unknown angle measures within a problem involving parallel lines and a transversal.

Supplementary angles are two angles whose measures add up to 180°.

Complementary angles are two angles whose measures add up to 90°.

EXAMPLE

Identify supplementary and complementary angles from the following list of angles.

∠A = 64°
∠B = 38°
∠C = 50°
∠D = 130°
∠E = 15°
∠F = 116°
∠G = 75°
∠H = 52°

Solution


The supplementary angles are:

  • ∠A and ∠F (64°+ 116° = 180°)
  • ∠C and ∠D (50° + 130° = 180°)

The complementary angles are:

  • ∠B and ∠H (38°+ 52° = 90°)
  • ∠E and ∠G (15° + 75° = 90°)


Now, it is your turn! Complete the questions in your Chapter 6, Lesson 2 Practice Makes Perfect that refer to Supplementary and Complementary Angles.



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