IM 7.7.2 Lesson: Adjacent Angles

• In one of the applets, drag the red point to draw a small half-circle in the middle of one side.

• Cut a straight line, starting from the center of the half-circle, all the way across the paper to make 2 separate pieces. (Your cut does not need to be perpendicular to the side of the paper.)

• On each of these two pieces, measure the angle that is marked by part of a circle. Label the angle measure on the piece.

Clare measured 70 degrees on one of her pieces. Predict the angle measure of her other piece.

       

• Draw a small quarter-circle in one of the corners.
• Repeat the previous steps to cut, measure, and label the two angles marked by part of a circle.

Priya measured 53 degrees on one of her pieces. Predict the angle measure of her other piece.

Use the protractor in the picture to find the measure of angles  and .

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

Use the protractor in the picture to find the measure of angles  and .

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

Angle  is a right angle. Find the measure of angle .

Point  is on line . Find the measure of angle .

• Try this yourself with any rectangular paper. Fold the left corner up at any angle, and then fold the right corner up so that the edges of the paper meet.

• Clare thought that the angle at the bottom looked like a 90 degree angle. Does yours also look like it is 90 degrees?

• Can you explain why the bottom angle always has to be 90 degrees? Hint: the third photo shows Clare’s paper, unfolded. The crease marks have dashed lines, and the line where the two paper edges met have a solid line. Mark these on your own paper as well.