Sector area from radians

We can calculate the area of a sector if we know the:

• radius of the circle
• angle of the sector (in radians)

The equation

A=\frac12\theta r^2

• A is the area of the sector
• \theta is the angle of the sector
• r is the radius of the circle

Finding the angle of the sector

We can rearrange A=\frac12\theta r^2 into:

\theta=\frac{2A}{r^2}

Finding the radius of the circle

We can also rearrange A=\frac12\theta r^2 into:

r=\sqrt{\frac{2A}{\theta}}