Acute, Obtuse, and Right

Jay Arcadi MED 300

Lesson Plan 3-28-07

Grade Level: 9th

Topic: Acute, obtuse, and right angles and triangles.

Materials: Chalkboard, chalk, protractors, and worksheets.

Lesson Overview: Students will take notes and work independently to create an understanding of acute, obtuse and right angles and triangles with the help of protractors.

Lesson Objectives: Students will be able to:

1. Students will be able to verbally justify the difference of acute, obtuse, right, and

straight angles.

2. Students will be able to verbally justify the difference of acute, equiangular, obtuse,

and right triangles.

3. Students will be able to use protractors as a tool to find measurements of angles.

New York State Standards: Key Idea 4 – Modeling/Multiple Representation

4A. Represent problem situations symbolically by using algebraic expressions, sequences, tree diagrams, geometric figures, and graphs.

Anticipatory Set: Have the students independently on a scrap sheet of paper; show what the following angles would look like. The students could draw them free handily and do not have to use rulers.

1) Angle greater than 0° and less than 90°

2) Angle that is 90°

3) Angle greater then 90° and less than 180°

4) Angle that is 180°

This will get the students to think about angles and their measures and see if they know how to use a right and straight angle to help them draw the angles. (5 min)

Developmental Activity:

First, past out the Classification of Angles and Triangles by Angles Notes. Then, fill in the blanks in the notes as a whole class, discussing with the students what they think should go into the blanks. Tell the students they can use notes to help them study or use them for reference. Next, pass out protractors and the Classification of Angles and Triangles by Angles worksheet. Have the students complete Part A from the worksheet with a partner or independently. Walk around the room making sure students are doing their work. Then have the students or groups share their answers with the whole class. Then have the students complete Part B of the same worksheet. Their may not be enough time do all the problems, so have them do the first three, and if there is enough time do the last three. Help any students that need help in using the protractors correctly. Also answer any questions they may have. Then go over the answers to the worksheet, by calling on students to share their answers with the whole class. (35 min)

Closure: With the whole class go over the all the definitions of the different types of angles and triangles from the notes. The type of angle depends on that angles’ measurement and the type of triangle depends on what angles it has. (5 min)

Assessment: Write the following questions (given below) up on the board. Then have the students answer the questions on a sheet of paper and hand it in at the end of class as an exit visa.

Assessment Questions:

How many acute angles can a triangle have?

How many right angles can a triangle have?

How many obtuse angles can a triangle have?

Name ______Date ______

Classification of Angles and Triangles by Angles Notes

Angles

1.) Acute-any angle which measures less than ____ º.

2.) Obtuse- any angle which measures more than ____ º, but less than ____ º.

3.) Right-any angle which measures exactly ____ º.

4.) Straight- any angle which measures exactly ____ º.

[1]

Triangles

1.) Acute- ____ angles measure ______than 90º.

2.) Obtuse- _____ angle measures ______than 90º.

3.) Right- _____ angle measures ______90º.

4.) Equiangular- _____ angles measure the ______, 60º.

[2]
Name ______Date ______

Classification of Angles and Triangles by Angles

Part A:

Directions:

Classify the type of angles as acute, obtuse, right or straight from the following picture:

<ABC: ______<EBC: ______

<FBC: ______<DBC: ______

<ABE: ______<ABF: ______

<ABD: ______<FBD: ______

Part B:

Directions:

Measure all the angles of each triangle and answer what type it is.

m<A: ______m<D: ______

m<B: ______m<E: ______

m<C: ______m<F: ______

Type of triangle:______Type of triangle: ______

m<G: ______m<J: ______

m<H: ______m<K: ______

m<I: ______m<L: ______

Type of triangle:______Type of triangle: ______

m<M: ______m<P: ______

m<N: ______m<Q: ______

m<O: ______m<R: ______

Type of triangle:______Type of triangle: ______

Answers

Notes:

Angles: 1) 90 Triangles: 1) all; less

2) 90; 180 2) one; more

3) 90 3) one; exactly

4) 180 4) all; same

Part A:

<ABC= Straight <EBC= Right

<FBC= Obtuse <DBC= Acute

<ABE= Right <ABF= Acute

<ABD= Obtuse <FBD= Obtuse

Part B:

Angles: Angles:

A= 65° D= 135°

B= 69° E= 21°

C= 46° F= 24°

Type: Acute Type: Obtuse

Angles: Angles:

G= 52° J= 37°

H= 90° K= 120°

I= 38° L= 23°

Type: Right Type: Obtuse

Angles: Angles:

M= 60° P= 90°

N= 60° Q= 62°

O= 60° R= 28°

Type: Acute or Equiangular Type: Right

Assessment:

How many acute angles can a triangle have? 2 or 3

How many right angles can a triangle have? Only 1

How many obtuse angles can a triangle have? Only 1

[1]http://regentsprep.org/Regents/math/angles/LAngles.htm

[2]http://regentsprep.org/Regents/math/angles/LAngles.htm