9.03 Angles and angle types

Lesson

Practice

Lesson

Are you ready?

Being able to identify the size of angle can help us in this lesson. Let's try this problem to review.

An angle of $90^\circ$90° is shown in the circle below.

What fraction of a full circle is this angle?
$\frac{1}{3}$13
A
$\frac{1}{4}$14
B
$\frac{1}{6}$16
C
$\frac{1}{8}$18
D

Learn

We can use this visual to remember the names for different angle sizes:

This video explains about acute, right, obtuse, straight, and reflex angles, as well as revolutions.

Apply

Select the $obtuse angle$ :

A
B
C
D

Remember!

A full revolution is made up of $360$360 degrees, and a single degree is written as $1^\circ$1°.

Angle type	Angle size
Acute angle	Larger than $0^\circ$0°, smaller than $90^\circ$90°.
Right angle	$90^\circ$90°
Obtuse angle	Larger than $90^\circ$90°, smaller than $180^\circ$180°.
Straight angle	$180^\circ$180°
Reflex angle	Larger than $180^\circ$180°, smaller than $360^\circ$360°.
Full revolution	$360^\circ$360°

Outcomes

4.G.A.1

Draw points, lines, line segments, rays, angles (right, acute, obtuse), and perpendicular and parallel lines. Identify these in two-dimensional figures.