### Mathematics Class IX

Number Systems
Polynomials
Coordinate Geometry
Lines and Angles
Triangles
Circles
Constructions
Heron’s Formula
Surface Areas and Volumes
Statistics
Probability

# Basic Terms and Definitions

1. Point – A Point is that which has no component. It is represented by a dot.

2. Line – When we join two distinct points then we get a line. A line has no endpoints it can be extended infinitely.

3. Line Segment – It is the part of the line which has two endpoints.

4. Ray – Ray is also a part of the line which has only one endpoint and has no end on the other side.

5. Collinear and Non-collinear points – Points lie on the same line are known as collinear points and the points that don’t lie on the same line are known as Non-Collinear Points.

Angles

When two rays begin from the same endpoint then they form an Angle. The two rays are the arms of the angle and the endpoint is the vertex of the angle.

Types of Angles

• Acute angle • Right angle • Obtuse angle : • Straight angle • Reflex Angle Complementary and Supplementary Angles

Complementary Angles are those which have the sum of two angles as 90°.

Supplementary Angles are those which have the sum of two angles as 180°.