Goal: My students will be introduced to many types of angles. They will be shown how to find the measurements of certain angles.

Objective: The students will be able to identify, define, estimate, measure angles (such as acute, right, obtuse, straight, complementary, supplementary, adjacent, vertical, and congruent).

Mind Set: Angles are seen in just about everything. Some people that use angles in their work are Architects and Constructors.

Lesson:

1. I will ask the class to tell me everything that they know about angles. I want to know all of the characteristic and measurements and anything else that you might know about them. I will write these down on the board.
2. I will teach the different kinds of angles and the characteristics of them. (use transparencies)

· Acute angles

1. Angle that measures between 0^o and 90^o

2. Examples: 30^o, 58^o, 88^o

· Right angles

1. Angle that measures exactly 90^o

2. A square in the corner represents it being a right angle

3. Example: (only one) 90^o

· Obtuse angles

1. Angle that measures between 90^o and 180^o

2. Examples: 93^o, 175^o, 100^o

· Straight angles

1. Angle that measures exactly 180^o

2. Looks like a straight line

3. Example: (only one) 180^o

· Complementary angles

1. Angles added together to equal 90^o

2. Example: 30^o + 60^o = 90^o

3. A + B = 90^o

· Supplementary angles

1. Angles added together to equal 180^o

2. Example: 132^o + 48^o = 180^o

3. A + B = 180^o

· Adjacent angles

1. Angles that share a common side and a common vertex

2. Do not have to be equal in measure but sometimes will be

3. A and B are adjacent angles but not congruent

· Vertical angles

1. Angles that are opposite from one another

2. Vertical angles will have the same measures

3. A = B

· Congruent angles

1. Angles that have the same measure

2. A B

3. Here are some examples in finding the measures of the angles. (See below)

Closure: Review the different types of angles by showing a picture of an angle and letting the students identify the angle type. I will also answer any questions that they might have.

Evaluation: (Due tomorrow) List 5 examples of each type of angle (acute, right, obtuse, and straight) that you find out in the world.

Grade Level: High school Geometry class (10^th – 12^th Graders)

Practice Problems: Directions: Find the measures of the following angles. (Answers in red and in degree measurements.)

1) These angles are complementary.

x + 4 + 2x – 10 3x – 6 3x x

= = = =

90 90 96 32

2)

2 (x + 10) + 3x + 10 2x + 20 + 3x +10 5x + 30 5x x

= = = = =

180 180 180 150 30

3)

3x + 5 + x 4x + 5 4x x

= = = =

125 125 120 30

4) Find the 3 remaining angles. (X, Y, Z)

Y

=

98

since W and Y are vertical angles, they are equal

180 – 92 82

= =

X X

X and Z are also vertical angles therefore they are equal

5) Solve for x.

2x – 5 2x x

= = =

35 40 20

X = 20

6)

4x – 17 3x x

= = =

X + 10 27 9

19