1. Go over the characteristics of an isosceles right triangle.
2. Select several tall objects on the school year and have pairs of students use the clinometer to estimate the object's height in the following manner:
   • A. Students use a clinometer and move toward or away from the objects being measured until an imaginary line from the student's eye to the top of the object forms a 45° angle (see illustration). Since the two sides in an isosceles right triangle are equal, Side A is equal to Side B in the figure.
   • B. Students measure the distance from where they are to the object by pacing or using a tape and add their height at eye level to determine the height of the object.
   • Compare the student's findings with the actual measurement. Discuss the merits of all the techniques for estimating heights and review possible reasons for the variation in answers.

Making the Clinometer

1. Use a straight piece of wood 8 to 10 inches long for a support.

2. Cut a half circle of heavy cardboard.

3. Use a protractor to add degree marks to the cardboard, marking zero at the point that is exactly perpendicular to the wood support.

4. Tack the cardboard to the center of the wood, making sure the top is parallel to the wooden straight edge.

5. Place a tack exactly in the center of the top of the cardboard.

6. Attach a weight to a string and suspend the string form the tack.