## Lesson Plan # 8 - Angle measurement, types of
angles and triangles

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- (5 min) Mental Math
- Start with 56, subtract 7, then divide by 7 [7]
- Divide 18 by 3, multiply by 2, then subtract 2 [10]
- Multiply 12 by 3, then subtract 6 [30]
- Add the following numbers: 8, 2 1/2 , 10 , 2 1/2 [23]
- What is the area of a triangle whose base is 10 inches and whose
height is 4 inches? [20 sq. in.]

- (5 min) Review of selected problems from Homework # 7 (<= 3
problems)

- (15 min) Introduce angle measurement and triangle types:

- Hand out the "Angle Measurement" handout.
- Explain angles and angle types as shown in the handout.
- Explain that the point of an angle is called its
*vertex*
- Explain "right" angle and the little box symbol.
- Ask what half of 90 is, then draw a 45 degree angle.
- Discuss the angle sequence at the bottom of the handout.
- Draw an angle on the board that is approximately 60 degrees, then
ask the class to estimate it's size. Answers should be between 45 and 90
degrees.
- Turn the handout over and discuss triangle types.
- Draw a [55,55,70] isoceles triangle on the board and ask the students
what type it is.

Note: you may want to break your discussion between the angle discussion
and the triangle discussion in order to do the first page of the in-class
exercise first before the triangle discussion.
- (Remainder of class) In-class Exercise.
- Hand out homework as students successfully complete the in-class
exercise.