Ans:- When a common vertex, arm and two lines either side of common arm is called Adjacent Angles.

Common Vertex, Arm, and Two Lines

When two lines intersect at a common point, they form angles. These angles are described based on their properties, including their vertex, arms, and the two lines on either side of the common arm.

Definition

When two lines intersect at a common point, the point of intersection is called the vertex of the angle. The vertex is the common endpoint of the two rays or line segments that form the angle.

Arms

The two rays or line segments that share the common endpoint are known as the arms of the angle. These arms extend from the vertex in opposite directions.

Lines on Either Side

The two lines that intersect at the vertex and create the angle are referred to as the lines on either side of the common arm. These lines can be extended indefinitely in both directions.

Angle Notation

Angles are typically labeled using three points: one on each arm and the vertex. The vertex is always the middle point. For example, an angle formed by lines AB and AC can be denoted as ∠BAC, where B is on one arm, A is the vertex, and C is on the other arm.

Types of Angles

Based on the measurement of the angle, it can be classified into various types:

1. Acute Angle: An acute angle measures less than 90 degrees.
2. Right Angle: A right angle measures exactly 90 degrees.
3. Obtuse Angle: An obtuse angle measures more than 90 degrees but less than 180 degrees.
4. Straight Angle: A straight angle measures exactly 180 degrees.
5. Reflex Angle: A reflex angle measures more than 180 degrees but less than 360 degrees.

Summary

When two lines intersect, they form angles. These angles are described by their vertex, arms, and the two lines on either side of the common arm. Understanding these components is essential in geometry as it helps classify and identify different types of angles.