501 Geometry Questions

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