Web-based Student Activities

Everything Geometry

Types of Angles

Students should be able to:

  • identify and describe the relative size of acute, obtuse and straight angles with respect to right angles.

What is an angle?

When two rays share an endpoint they form an angle. The point where the rays intersect is called the vertex of the angle. The two rays are called the sides of the angle. Acute Angles

An acute angle is one that rotates less than 90 degrees. You can tell an angle is acute when it has a measure between 0 and 90 degrees.

Click the button below the angle to make the ray rotate to show the how big an acute angle can be.

Click on the play button above to watch the letter N flip, or reflect. Click on the play button to watch it again.

Examples of Acute Angles

Any angle that opens less than 90 degrees is acute, no matter what direction it if facing.

acute angles

Obtuse Angles

An obtuse angle is one that rotates more than 90 degrees but less than 180 degrees. You can tell an angle is obtuse if it has a measure like 95 degrees or 135 degrees.


Click the button below the angle to make the ray rotate to show the how big an obtuse angle can be.

H

Click on the play button above to watch the letter H slide, or translate. Click on the rewind button to watch it again.

Think About It

Look at the two H's above. Imagine you had not seen the slide take place and I told you that this was an example of a flip (reflection). Would this be true or false? (Click one of the buttons below)

True

False

Examples of Obtuse Angles

obtuse angles

Click on the play button above to watch the letter W slide, or translate. Click on the rewind button to watch it again.

Right Angles

When an angle rotates 90 degrees, the angle is called a right angle. The two rays that form the angle are said to be perpendicular.


Click the button below to make a right angle. Notice the box symbol that is used to show that the angle is a right angle, or has a measure of 90 degrees.

T

Click on the play button above to watch the letter T turn, or rotate. Click on the rewind button to watch it again.

Examples of Right Angles

A
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