# Angles

The inclination of one line to another. One complete revolution equals 360° (degrees) or 2*π* radians.

The five types of angles are zero, acute, right, obtuse, and straight.

An angle starts at the initial side and ends at the terminal side

if this is anti-clockwise then the angle is positive

if this is clockwise then the angle is negative

### Flat

An informal unit of angle measure equal to 1/6 turn or 60°. This comes from the fact that hexagonal nuts have 6 flat sides; to turn the nut *one flat* is to turn it 1/6 revolution.

**See also: **Acute Angle, Angle Bisector, Corresponding Angles, Coterminal Angles, Initial Side, Obtuse Angle, Plane Angle, Protractor, Radian, Reflex Angle, Right Angle, Rise Run, Same Side Exterior Angles, Same Side Interior Angles, Straight Angle, Supplementary Angles, Terminal Side, Vertical Angles, Zero Angle.

**Subjects: ** Geometry Trigonometry