Overview
This lecture covers complementary and supplementary angles, their definitions, and methods for finding missing angles, using example problems for each concept.
Complementary Angles
- Complementary angles are two angles that add up to exactly 90 degrees.
- To find a missing complementary angle, subtract the known angle from 90 degrees.
- Example 1: Given 70°, missing angle x = 90° - 70° = 20°.
- Example 2: Given 48°, missing angle y = 90° - 48° = 42°.
Supplementary Angles
- Supplementary angles are two angles that add up to exactly 180 degrees.
- To find a missing supplementary angle, subtract the known angle from 180 degrees.
- Example 3: Given 65°, missing angle a = 180° - 65° = 115°.
- Example 4: Given 128°, missing angle z = 180° - 128° = 52°.
Memory Tip
- Remember: "C" in complementary comes before "S" in supplementary; 90° (complementary) is less than 180° (supplementary).
Key Terms & Definitions
- Complementary angles — Two angles whose measures add up to exactly 90 degrees.
- Supplementary angles — Two angles whose measures add up to exactly 180 degrees.
Action Items / Next Steps
- Practice finding missing complementary and supplementary angles using subtraction.
- Memorize the definitions and differences between complementary and supplementary angles.