
Radius
Circle Basics
A radius is essential in geometry for calculating area and circumference of a circle.
Find the area of a circle by using the radius in the formula Area = πr^2.
Measure Twice
Always double-check the length of a radius, as even a small error changes the circle size significantly.

She carefully measured the radius again before cutting the round cake board.
Not a Diameter
Do not confuse radius with diameter; the radius is half the length of the diameter.

The diameter is twice the radius, so if the radius is 4 cm, the diameter will be 8 cm.
Compare with
AreaCircumferenceDiameterExtentReachScopeSpanSweep
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