Radians
Natural angle measure.
Definition. One radian = the angle subtended at the centre of a circle by an arc equal in length to the radius.
Why radians? Calculus formulae (like ) only work in radians.
Key conversions.
- rad = .
- rad = .
- rad = .
- rad = .
- rad = .
Conversion formulae.
- Degrees → radians: multiply by .
- Radians → degrees: multiply by .
Cambridge tip. Memorise the table of common angles in radians.
- rad = .
- Required for calculus.
- Memorise common angles.