Written by Jerry Ratzlaff on . Posted in Plane Geometry

### Radius of a Circle formula

$$\large{ r = \frac {D} {2} }$$

$$\large{ r = \frac {C} {2 \pi} }$$

$$\large{ r = \sqrt {\frac {A} {\pi} } }$$

Where:

$$\large{ r }$$ = radius

$$\large{ d }$$ = diameter

$$\large{ C }$$ = circumference

$$\large{ A }$$ = area