Types of Angles

An angle is comprised of two rays that share the same endpoint. The two rays are called thearms of the angle. The point where the arms intersect is called the vertex. Look at the following example.

Source: (Tutor Vista:http://www.tutorvista.com/content/math/geometry/angles_at_a_point/class9maths2.php)

and are called arms of the angle BAC. The point 'A' is called the vertex. The angle formed by the two rays AB and AC is represented by the symbol BAC. . If there is only one angle at A, then the angle BAC may be represented by

An angle measures the amount of rotation in degrees. There are six types of angles:

- Acute angle: angle that is less than 90°.
- Right angle: angle that is exactly 90°.
- Obtuse angle: angle between 90°-180°.
- Straight angle: angle that is exactly 180°.
- Reflex angle: angle between 180°-360°.
- Revolution: a 360° angle, a full rotation.

The following images are examples of each type of angle.

source: (math is fun: www.mathsisfun.com/geometry/index.html)

Now, its your turn, try it yourself!

Look at the image below and answer the following questions to practice and work on what you have just learned.

Source: (Tutor Vista:http://content.tutorvista.com/maths/content/geometry/lines%20angles%20triangles/images/img42.gif)

1. How many acute angle(s) are there? Name three.

2. How many obtuse angle(s) are found? Name 3.

3. How many right angle(s) are found? Name them.

4. How many reflex angle(s) are found? Name them.

5. Name the straight angle.

6. Give an example of a full rotation angle.

source: (CSL Cartoonstock: http://www.cartoonstock.com/directory/A/Angles.asp)