Pairs of angles formed where two lines intersect. These angles are formed by rays pointing in opposite directions, and they are congruent. Vertical angles come in pairs.

The point on a segment that lies exactly halfway from each end of the segment. The distance from the endpoint of a segment to its midpoint is half the length of the whole segment.

a line segment connecting two points on a circle; not "do re mi"

A line segment whose endpoints are both on a circle. Not a collection of musical notes.

Any segment from one point on a circle to another. Despite what you might think, they aren't all that musical.

**4. What is parallel Postulate?**

A postulate which states that given a point not located on a line, exactly one line passes through the point that is parallel to original line.

**5. What is common Denominator?**

the bottom part of fractions; in this case when more than one fraction has the same bottom as all the others

A unit of measure for the size of an angle. One full rotation is equal to 360 degrees. A right angle is 90 degrees. One degree equals radians.

angles that share a side

Two angles that share both a side and a vertex. They stick by each other through and through.

**8. What are complementary Angles?**

Angles that add up to 90°

Two wrongs don't make a right, but two complementary angles do. They're two angles that add up to 90° exactly.

Two angles that add up to 90°. Two wrongs don't make a right, but two complementary angles sure do.

A ray that shares a common vertex with an angle, lies within the interior of that angle, and creates two new angles of equal measure.

A ray, one of a pair, that shares a common vertex with an angle, lies within the interior of that angle, and creates, with its partner, three new angles of equal measure. Angle trisectors come in pairs.