What is a Radian?
Radian
One radian is the angle subtended at the centre of a circle by an arc whose length is equal to the radius of that circle.
Radians are the natural unit of angle measurement in mathematics — they link angle directly to the geometry of the circle itself, rather than an arbitrary division into 360 parts.
Some key reference facts:
- A full revolution around a circle = radians =
- A straight angle = radians =
- A right angle = radians =
Analogy
Think of it this way: if you bent a piece of string equal in length to the radius of a circle and laid it along the circumference, the angle formed at the centre would be exactly 1 radian. You'd need just over 6 of those () to go all the way around.
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