Determine the equation of the circle if its centre is at the origin and radius 3.

Find the equation of the circle whose centre is (-3, 2) and radius 4.

Find the equation of the circle with the centre (1/2,1/4) and radius 1/2 .

In the following ,find the equation of the circle with:- centre (-2,3) and radius 4

Find the equation of the circle whose centre is (a cos alpha, a sin alpha) and radius is a.

Show that the points A(1, 0), B(2, -7), C(8, 1) and D(9,-6) all lie on the same circle. Find the equation of this circle, its centre and radius.

Find the equation of the circle whose centre is the point (1,-2) and which passes through the centre of the circle x^2 + y^2 + 2y = 3 .

Find the equations of the following circle : Centre (0, 2) and radius 2.

In the following ,find the equation of the circle with:-centre (0,2) and radius 2