Lines and Angles Class 9 Notes Maths - Chapter 6

Chapter: 6

What Are Lines And Angles ?

Collinear And Non-collinear Points

• If three or more points lies on the same line then they are called collinear points.

• It the points are not collinear then we can say they are non-collinear points.

• Two points are always collinear.

Parallel And Intesecting Lines

• Two lines are said to be intersecting, if they intersect each other at one point.

• Lines which do not intersect are called parallel lines.

An Important Fact

Lines which are parallel to the same line, are parallel to each other.

Some Important Facts

• If a ray stands on a line, then the sum of the adjacent angles so formed is 180°, i.e., the sum of the linear pair of angles is 180°.

• If two lines intersect each other, then the vertically opposite angles are equal.