Geometry
Sector area and arc length
Both are simply the corresponding whole-circle quantity scaled by the fraction of the turn.
The Formula
Sector A = pi r^2 x angle/360, arc L = 2 pi r x angle/360
Both are simply the corresponding whole-circle quantity scaled by the fraction of the turn.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| angle | Central angle of the sector | degrees | In degrees. 360 gives the whole circle back. |
What Each Symbol Means
angledegrees
Central angle of the sector
In degrees. 360 gives the whole circle back.
See It Worked With Real Numbers
A formula on its own does not tell you which number goes where. The how to calculate the area of a circle page applies this equation to a concrete case, shows every intermediate step, and names the mistakes that produce a wrong answer even when the algebra is right.
Where This Formula Appears
This equation is the working core of How To Calculate The Area Of A Circle, filed under Math. Every number the guide produces comes from substituting into this one line.