Substitute the value of the radius into the formula for the area of a circle. Multiply π by the square of the radius. This is the same as π × 𝒓 × 𝒓. The formula for the area of a circle ...

This means that, using Pythagoras’ theorem, the equation of a circle with radius \(r\) and centre (0, 0) is given by the formula \(x^2+ y^2= r^2\). Find the equation of a circle with radius 3 ...