Objective:

Students will draw angles and estimate the measures of angles

(9-2).

Vocabulary

• Straightedge – a ruler or any object with a straight side, which can be used to draw a line.

Steps to draw an angle• Step 1 draw 1 side of the angle. Then mark the

vertex and draw an arrow.

• Step 2 place the protractor along the side as you would to measure an angle. On the protractor, find the number of degrees needed for the angle you are drawing and make a pencil mark at the degree.

• Step 3 with a straightedge, draw the side that connects the vertex and the pencil mark. Draw an arrow on the end of the other side.

Examples

• Draw a 68° angle.

Mark the vertex and draw an arrow.

Examples

• Draw a 68° angle.

Mark the vertex and draw an arrow.

Find 68° on the appropriate scale. Make a pencil mark.

.

Examples• Draw a 68° angle.

Mark the vertex and draw an arrow.

Find 68° on the appropriate scale. Make a pencil mark.

Draw the side that connects the vertex and the pencil mark.

.

ExamplesThe circle graph shows the results of a

survey of music preference among 6th graders at Pine Middle School. Use the measures of the angles to order the types of music from most preferred to least preferred.

Explore You need to order the types of

music from most to least

preferred.

oldiesrap

country rock

ExamplesThe circle graph shows the results of a

survey of music preference among 6th graders at Pine Middle School. Use the measures of the angles to order the types of music from most preferred to least preferred.

Explore You need to order the types of

music from most to least

preferred.

Plan Use a protractor to measure the

angles that are too close to estimate.

Then order from greatest to least.

oldiesrap

country rock

Examples

Explore You need to order the types of music from most to least preferred.Plan Use a protractor to measure the angles that are too close to estimate. Then order from greatest to least.Solve Oldies is shown by the smallest angle. It is least preferred. Country is shown as the largest angle. It is most preferred. The measure of the angle for rock is 85°. The measure of the angle for rap is 90°. So the 6th graders prefer country, rap, rock, and oldies.

oldiesrap

country rock

Explore You need to order the types of music from most to least preferred.Plan Use a protractor to measure the angles that are too close to estimate. Then order from greatest to least.Solve Oldies is shown by the smallest angle. It is least preferred. Country is shown as the largest angle. It is most preferred. The measure of the angle for rock is 85°. The measure of the angle for rap is 90°. So the 6th graders prefer country, rap, rock, and oldies.Examine Find the measure of each angle. Then add. The total should be 360°. 140° + 90° + 85° + 45° = 360°

oldiesrap

country rock

Guided PracticeUse a protractor and a straightedge to draw

angles that have the following measurements.

120°

25°

43°

Use a protractor and a straightedge to draw angles that have the following measurements.

120° 25°

43°

Guided Practice

• Estimate the measurement of each angle.

Guided Practice

• Estimate the measurement of each angle.

about 120° about 90°

Guided Practice

Is the measure of angle ABC greater than, less than, or about equal to 155°?

C

A B

Guided Practice

Is the measure of angle ABC greater than, less than, or about equal to 155°?

C A B

about equal to