Contents

Lines & line segment

Angles

Angle Properties of straight lines

Angle Properties of Parallel Lines

Quiz

Geometry Main Page 

Lines & Line Segments

Line segment

When we mark two points and join them with a straight line, we will get a line segment. The two points we marked are called endpoints. If we name these two points A and B, we will get a line segment AB. 

The ruler is used for measuring length and drawing line segment. The measurement of length should start from the zero mark in the ruler.

Line

If we extend the line segment in both directions on and on without end, we will get what is called in Euclidean Geometry, a line.

Line segment AB, line AB and length of AB may simply be written as AB. Instead of using different ways to show them, we simply represent them like this:

Perpendicular Line

When two line segment cut to form right angles (90°), we say that the line segment are perpendicular to each other.

Parallel Lines

Two straight lines are parallel if they are both perpendicular to another straight line. In other words, when two straight lines in a plane do not intersect, the lines are parallel.