Measuring angles

1 Full revolution = 360 ° 

                                     Degree

We measure angles in term of degrees.

  1 revolution = 360 °

  1/2 revolution = (360°)/2 = 180°

  1/4 revolution = (360°)/4 = 90°

So,

  Right angle =  1/4 revolution = 90°

  Straight angle = 1/2 revolution = 180°

Acute Angle

Acute angle is less that right angle.

∴        Acute angle < Right Angle.

          Acute angle < 90°

Obtuse Angle

Obtuse angle is greater than right angle, but smaller than straight angle.

Right angle < Obtuse angle < Straight angle.

90° < Obtuse angle < 180°

Reflex Angle

Reflex angle is an angle greater than straight angle.

  Reflex angle > Straight angle

  Reflex angle > 180°

To summarize,

  Right angle = 90°

   Straight = 180°

  Acute angle < 90°

  Obtuse angle > 90° & Obtuse angle < 180°

  Reflex angle > 180°