# CLASS-4GEOMETRY-ANGLE

ANGLE -

Introduction Of Angle -

Angles are geometric figures formed by two rays that share a common endpoint called a vertex. The two rays are called the sides of the angle. Angles are measured in degrees, with a full circle being 360 degrees. Angles can be classified according to their size or shape.

Some common types of angles include:

• Acute angle: An angle that measures less than 90 degrees.
• Right angle: An angle that measures exactly 90 degrees.
• Obtuse angle: An angle that measures more than 90 degrees but less than 180 degrees.
• Straight angle: An angle that measures exactly 180 degrees.
• Reflex angle: An angle that measures more than 180 degrees but less than 360 degrees.
• Complementary angles: Two angles whose measures add up to 90 degrees.
• Supplementary angles: Two angles whose measures add up to 180 degrees.

Angles are used in many fields, including mathematics, engineering, and physics, and are an important concept in trigonometry, which deals with the relationships between angles and sides of triangles.

Angle -

-  Two rays starting from a common point form an angle.

-  The two rays are called the arms or sides of the angle.

-  The meeting point of the arms of the angle is called the vertex. -  An angle is denoted by the symbol .

-  An angle is named by three capital letters. The letter at the vertex always comes in between the other two letters. The given angle is named as ∠ AOB or ∠ BOA. Vertex O is at the middle of P and R.

The unit for measuring angles is degree. The symbol for degree is °.

The ere are some type of angles are given below with picture for your better understanding -

1. ACUTE ANGLE :- An angle whose measure is less than 90° is called an acute angle.

Examples : 30°, 45°, 84°

2. RIGHT ANGLE :- An angle whose measure is 90° is called a right angle.

3. OBTUSE ANGLE :- An angle which measures more than 90° but less than 180° is called an obtuse angle.

Examples : 120°, 135°, 175°.

4. STRAIGHT ANGLE :- An angle whose measure is 180° is called a straight angle.

5. REFLEX ANGLE :- An angle whose measure is greater than 180° but less than 360° is called a reflex angle.

Examples : 210°, 195°, 340°

6. COMPLETE ANGLE :- An angle whose measure is 360° is called a complete angle.