Open Microsoft Excel. Type "=Diameter/2" without quotes in cell A1, replacing "Diameter" with the known diameter of the circle. Press "Enter" to calculate the radius in the same units used for ...

This means that, using Pythagoras’ theorem, the equation of a circle with radius \(r\) and centre (0, 0) is given by the formula \(x^2+ y^2= r^2\). Example Find the equation of a circle with ...

The radius of the first circle is shown as 3cm. They then increase by 2cm each time: 5cm → 7cm → 9cm → 11cm. So, the radius of the largest circle is 11cm.