Angles and Their Types

Angles.

When two straing lines meet at a point they are said to form a angle.

Acute Angle

The angle which is less than 90 degree is called acute angle.

Obtuse Angle

The angle which is greater than 90 degree but less than 180 degree.

Straight Angle

The angle which is equal to 180 degree is called straight angle.

Reflex Angles

Reflex angles are greater than 180 degree but less than 360 degree.

Adjacent Angles.

The angles which lies on either side of a common arm. 

Right Angles.

Are equal to 90 degree.

Complementary Angles

When two angles together make 90 degree, they are said to be complementary. 

Supplementary Angles

When two angles together make 180 degree, they are said to be supplementary.

Measurement of Angles.

We usually measure angles in degrees. A degree is a unit of angular measure. We may define it as one-ninetieth of the angular space between two lines at right angles to each other. 

For the measurement we use the units,

                60 Seconds = 1 Minute

                60 Minutes = 1 Degree

                60 Degrees = 1 Right Angle.

Angles Measuring Instruments 

Protacotrs.

Protactors are used to measure the angles from 0 to 180 degrees. They are usually either semicircular or rectangular in shape. 

Set Squares.

Set squares are also used to measure the angles like 30,45,60 and 90 degrees. Set square can be used singly and together.