~ 7.2 ~

Adjacent Angles

Learning Targets

  • I can find unknown angle measures by reasoning about complementary or supplementary angles.

  • I can recognize when adjacent angles are complementary or supplementary.

Notes

If two angle measures add up to 90°, then we say the angles are complementary. Here are three examples of pairs of complementary angles.

If two angle measures add up to 180°, then we say the angles are supplementary. Here are three examples of pairs of supplementary angles.

Vocabulary

complementary

Complementary angles have measures that add up to 90 degrees.

For example, a 15° angle and a 75° angle are complementary.

supplementary

Supplementary angles have measures that add up to 180°.

For example, a 15° angle and a 165° angle are supplementary.

adjacent angles

Two angles are adjacent when they have a common side and a common vertex (corner point) and don't overlap. In regular English, adjacent means "next to".

Activities

2.1 Estimating Angle Measures

Estimate the degree measure of each indicated angle.

2.3 Is It a Complement or Supplement?

  1. Use the protractor in the picture to find the measure of angles:

      • BCA

      • BCD

      • Explain how to find the measure of angle ACD without repositioning the protractor.

  2. Use the protractor in the picture to find the measure of angles:

      • LOK

      • LOM

      • Explain how to find the measure of angle KOM without repositioning the protractor.

  3. Angle BAC is a right angle. Find the measure of angle CAD.

  4. Point O is on line RS. Find the measure of angle SOP.

Add to Your Notes

What does it mean for two angles to be supplementary?

  • Their sum measures to 180°.

What does it mean for two angles to be complementary?

  • Their sum measures to 90o.

If you know two angles are supplementary and you know the measure of one angle, how can you find the other?

  • Subtract the angle you know from 180o.

Assignment

Check Google Classroom!