Radian rad
About the Radian
A radian is the angle subtended at the centre of a circle by an arc equal in length to the radius, so a full turn is 2π radians. Because it is a ratio of two lengths it is dimensionless. Mathematics and physics prefer radians because derivatives of trigonometric functions take their simplest form in them.
Related Units
Steradian
sr1 sr = 1 m²/m² (dimensionless)
The steradian is the solid angle that cuts out an area equal to the square of the radius on the surface of a sphere. A...
Degree of arc
°1° = π/180 rad
A degree is one 360th of a full turn. The number 360 traces to Babylonian astronomy and its base-60 number system...
Hertz
Hz1 Hz = 1 s⁻¹
The hertz is one cycle or event per second and replaced the older expression cycles per second. It is named after...
Newton
N1 N = 1 kg·m·s⁻²
One newton is the force that accelerates a mass of one kilogram at one metre per second squared. It is named after...