Those Obtuse Angles are aCute, Right?

Sheryl Davis

Content Area: Geometry and Measurement

Grade Level: 4th grade Summary: The purpose of this Instructional PowerPoint is to teach students how to classify angles as obtuse, right, or acute.

Learning Objective: Given a picture of an angle, students will classify the angle as obtuse, right, or acute with 100% accuracy.

Content Standard: GLE 0406.4.1 Understand and use the properties of lines, segments, angles, polygons, and circles.

Accomplishment: Identify acute, obtuse, and right angles in 2-dimensional shapes.

Let’s Begin

Angles are all around

us

The panes on a window

The frame on a gate

A suit lapel

What is an angle?

?

? ?

?

Two rays…

That share the same endpoint (vertex)…

Form an angle

The area inside the two rays makes up the INTERIOR ANGLE

Click on the interior angle (the green area) to learn more.

↗

→

↘

To infinity

Ready to move on?

When we measure an angle, we can classify it as:

RIGHTACUTE

OBTUSEAngle measures

90°

Angle measures less than 90°

Angle measures greater than 90°

RIGHT ANGLE

• A right angle is an angle measuring exactly 90°

ACUTE ANGLE

• An acute angle is an angle measuring less than 90°

OBTUSE ANGLE

• An obtuse angle is an angle measuring more than 90°

Go to the following websiteManipulate the angle to form

a right angle, acute angle, and obtuse angle

http://www.mathopenref.com/angleright.html

Click on the right angle And learn a song to help youRemember right, acute, and

obtuse angles

Time to play…

NAME

THAT

ANGLE!!!

Click on the correct name for the following angle

Right Angle Acute Angle

Obtuse Angle

OOPS!! TRY AGAIN

Click on the correct name for the following angle

Right Angle

Obtuse Angle

Acute Angle

OOPS!! TRY AGAIN

Click on the correct name for the following angle

Right Angle

Obtuse Angle

Acute Angle

OOPS!! TRY AGAIN

SummaryIn this lesson, students will have learned:

Angles are not just lines on a page. Everyday objects, such as a window pane or a frame on a gate, are made up of angles.

Two rays that share the same endpoint, or vertex, is an angle. The area between the rays is called the interior angle.

We can measure angles and classify them accordingly.

Right angles measure exactly 90°, acute angles measure less than 90°, and obtuse angles measure more than 90°.

Students will visit two interactive websites where they will explore the properties of an interior angle and manipulate the measurement of an angle to form right, acute, and obtuse angles. They will also visit a website that includes a song sung to the tune of Old McDonald to help them remember the properties of right, acute, and obtuse angles.