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 angel 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°