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:

$1 rad \approx 57.3°$
A full revolution around a circle = $2 π$ radians = $360°$
A straight angle = $π$ radians = $180°$
A right angle = $\frac{π}{2}$ radians = $90°$

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 ( $2 π \approx 6.28$ ) to go all the way around.

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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:

$1 rad \approx 57.3°$
A full revolution around a circle = $2 π$ radians = $360°$
A straight angle = $π$ radians = $180°$
A right angle = $\frac{π}{2}$ radians = $90°$

Analogy

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SL 3.4—Circle, radians, arcs, sectors

What is a Radian?

9 more sections in this topic

SL 3.4—Circle, radians, arcs, sectors

What is a Radian?

9 more sections in this topic