*/line - линия; line segment - отсечка; ray - лъч; angle - ъгъл; /*

When two **rays** share a **point** they form an **angle**.

## Slope

A **slope** of a line is the change in

To find the slope of

If the slope of a line is *zero*, then the line is perfectly horizontal.

If the slope of a line is *undefined*, then the line is perfectly vertical.

If a line is perfectly vertical & another line is perfectly horizontal, then the lines are perpendicular to each other.

### Parallel lines

If the slopes of two lines are equal, then they are parallel.

### Perpendicular lines

If the slope of one line is the negative and reciprocal of the another line, then the two lines are perpendicular.

## Distance

### In two-dimension

The distance between two points in the second dimension can be found using:

### In three-dimension

### Midpoint

The midpoint of a **line segment** is the point that is *equidistant* from both endpoints of the line segment. It **bisects** the segment.

To find the midpoint of a line segment