Angles:
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.