Angles:
In geometry, an angle is the figure formed by two rays, called the sides of the angle, sharing a common endpoint, called the vertex of the angle. Angles formed by two rays are also known as plane angles as they lie in the plane that contains the rays.
1. What is angle?
Ans: two lines from a vertex make a shape called an angle.
Two rays with a common end point form an angle. An angle is also formed when two line segments meet or cross.
2. Right angle:
An angle which is equal to 90 degrees, one quarter of a full revolution is called right angle.
3. Acute angle:
An angle which is less than 90 degrees or right angle is called acute angle.
4. Obtuse angle:
An angle which is more than 90 degrees but less than 180 degrees
5. Point:
An exact location on a plane is called a point.
How is an Angle Measured?
Degree is the unit by which an angle is measured. It is defined as 1/360 of a complete revolution. Thus, one complete revolution about a point is 360. We can measure angles with a protractor.
a) Adjacent Angles:
Two angles, which lie side by side such that one of their arms and the vertex is common, are called angles.
Vertically Opposite Angle:
In the figure, AOB and COD are straight lines. Calculate the value of a and b.