**Line:-** A set of infinite points with length but no width. A line has no endpoint.

**Line segment:- ** A line segment is similar to a line with two endpoints

**Ray:- **A ray is also similar to a line with one endpoint.

**Types of Lines**

**Parallel lines:-** If two lines have **no point in common** they are said to be parallel to each other.

**Intersecting lines:-** If two lines** intersect at a point** they are said to be intersecting lines.

**Perpendicular lines:-** If two lines **one vertical and the other horizontal intersect at a point **they are said to be perpendicular lines.

**Concurrent lines:-** If **more than two lines intersect at a common point** they are said to be concurrent lines.

**Angle:- **Angle is defined as a figure formed when two rays meet at a point. It is represented by the symbol **∠**. In the figure, the angle is **∠AOB. Point O **is the vertex.

**Degree ⇔ Radian Conversion**

Angle is usually denoted by degree (°) like 0°, 45°, 90° 180° etc. It can also be represented by radian. To convert radian to degree or vice-versa it is recommended to learn the value of **pi (π)** in radian and degree. The value of** π is 3.14 (22/7) in radian** and** 180° in degree.**

Thus **3.14 radian = 180° **[use unitary method for conversion] (1 radian = 180°/ 3.14 **OR** 1° = 3.14/180 )

**Types of Angle**

**1) Acute Angle: **Angles whose value is** less than 90°** are called Acute Angle.

**2) Right Angle: **Angles whose value is **equal to 90°** are called Right Angle.

**3) Obtuse Angle: **Angles whose value is** greater than 90° but less than 180°** are called Obtuse Angle.

**4) Straight line: **When the value of **angle is 180°** it becomes a straight line.

**5) Reflex Angle: **Angles whose value is** greater than 180° but less than 360°** are called Reflex Angle.

**6) Complementary Angles: **When the** sum of the measures of the two angles is 90°, **the angles are called Complementary Angle.** ∠A + ∠B = 90°**

**7) Supplementary Angles: **When the** sum of the measures of the two angles is 180°, **the angles are called Supplementary Angle.**∠A + ∠B = 180°**