Find the equation of a circle whose centre is (1,2) and radius 2.

Find the equation of the circle whose centre is (2, 3) and which touches the line 3x - 4y - 1 = 0.

Find the equation of the circle whose centre is (4, 5) and which passes through the centre of the circle x ^2 + y ^2 + 4x -6y - 12 = 0

Find the equation of a circle whose centre is the origin and passes through the point (2,-4).

Find the equation of a circle with centre(2,2)and passes through the point (4,5).

write down the equation of the circle whose centre is the point (-2, 3) and radius is of lenght of 5 units.

Write down the equation of the circle whose centre is the point (2, -3) and radius is 5 units.

If OABC is a quadrant of a circle whose centre is O and radius r, find the perimeter of the circle.

Find the coordinates of a point A,where AB is the diameter of a circle whose centre is (2,-3) and B is (1,4).

Find the equation of the circle whose radius 4 and which is concentric with the circle x ^2 + y ^2 + 2x - 6y = 0.

Find the equation of the ellipse whose vertices are (0,+-6) and eccentricty is 1/3.