ANGLES

An angle is formed by two line segments or 2 rays that share the same endpoint (called the vertex).

T is the vertex.

An angle formed by rays – named angle T or named angle CTA or angle ATC.

We use the following symbol for the word angle:

Here are 5 classifications of angles:

Right angle 90 °

Acute angle: Between 0 & 90 °

Obtuse angle: Between 90° & 180 °

Straight angle = 180 °

Reflex angle: Between 180° & 360 °

Pairs of angles:

Vertical angles :

Angles that are opposite each other. Vertical angles have the same measure in degrees. In the figure above, angles 1 and 3 are vertical angles. Angle 3 = 60°, and therefore angle 1 = 60°.

Angles 2 and 4 are also vertical angles. Can you figure out the measure of angles 2 and 4?

(Hint: read about ‘supplementary angles below.)

Adjacent angles:

Adjacent angles are angles that are next to each other. Angles 1 and 2, 3 and 4, 2 and 3, and 1and 4 are all adjacent angles.

Supplementary angles are two angles whose measures add up to 180°. Angles 1 and 2, 3 and 4, 2 and 3, and 1and 4 are all supplementary angles.