Understanding Elementary Shapes

• One complete turn of the hand of a clock is one revolution. The angle of one revolution is called a complete angle.

• A right angle is of a revolution and a straight angle is  of a revolution.

• 1 complete angle = 2 straight angles = 4 right angles
• 1 straight angle = 2 right angles 
• If an angle measures less than a right angle then it is known as an acute angle.

The following angles are acute: 

• If an angle measures more than a right angle but less than a straight angle, then it is an obtuse angle.

The following angles are obtuse: …