360° or 90° and is called a rig and BO of the angle are sai each other since they form a ri

=

the angle AOC 180° and th counter-clockwise is 270°. The a wise (as indicated by the dotted AOE in the lower figure is equ and is 23 of 90° or 60°, and ar

Every degree contains 60 m contains 60 sec. ("). One-sev 14 of 90° or 1264° or 12° 5134' A horizontal line is one whic as the horizon, as line AC, Fig. A vertical line is one perpend as BD, Fig. 28.

To bisect an angle or a line m equal parts. To trisect mean. equal parts.

An angle not a right angle i An acute angle is one less th obtuse angle is one greater than

PROBLE

1. If two straight lines intersect a angle, what kind of angles are the oth figure.

2. In Fig. 29, if the two straight lin relation have the angles AOC and