501 Geometry Questions

Classifying Angles

Angles are measured in degrees, which are a measurement of how much
one side of an angle is rotated away from the other side. Degrees do not
measure distance or length. The symbol used for degrees is °. Remember
that angles are usually named with three letters, starting with a point on one
side, followed by the vertex point, and ending with a point on the other side.
It doesn’t matter which side is named first. The following angle can be
named ∠RSB or ∠BSR.

If a given vertex is a vertex for only one angle, than that point can be used
to name the angle as well. For example, in the previous figure, ∠RSB can
also be called ∠S. In the following angle, ∠A cannot be used as a name
because point A is the vertex for ∠KAS as well as for ∠KAM. Therefore if
∠A was used, it would not be clear which angle was being referred to.

Angles are classified by their relationship to the degree measures of 90°
and 180°:
Straight angles:An angle that measures 180° will look like a straight line
and is called a straight angle.

Right angles:An angle that measures 90° is called a right angle. Right
angles have their own symbol to show they are 90°. A small square is drawn

Figure 2.3

A B C

Figure 2.2

A

K

M S

S

R

B

Figure 2.1

501 Geometry Questions