The formula to find the area of a circle is to square the radius and multiply by π. The inverse of this is divide the area by π, then square root. π𝒓² = 400. 3۰14 × r² = 400 ...

To find the equation of a circle when you know the radius and centre, use the formula (x a) 2 + (y b) 2 = r 2, where (a, b) represents the centre of the circle, and r is the radius.