at the vertex of right angles to note their unique nature, as shown in Fig-
ure 2.4.
Acute angles:An angle that is larger than 0° but smaller than 90° is called
an acute angle. (A clever way to remember this is to think, “What a cute
little angle!”)
Obtuse angles:An angle that is larger than 90° but smaller than 180° is
called an obtuse angle. (Do you like rhymes? “That obtuseis as big as a
moose!”)
Reflex angle:An angle that is larger than 180° but smaller than 360° is
called a reflexive angle. There are no names for angles larger than 360°.
A Figure 2.7
B C
180 < m∠ABC < 360°,
REFLEX
Figure 2.6
B
A
C
90 < m∠ABC < 180°,
OBTUSE
B
A
C
0 < m∠ABC < 90°
ACUTE
Figure 2.5
Figure 2.4
m∠ABC = 90°,
RIGHT
B
A
C
501 Geometry Questions