Find the equation of a circle with radius 3 units and centre (0, 0). The radius, \(r = 3\) and \(r^2 = 9\), so the equation of the circle is \(x^2 + y^2 = 9\). What is the radius of the circle given ...

Any point P with coordinates (\(x,~y\)) on the circumference of a circle can be joined to the centre (0, 0) by a straight line that forms the hypotenuse of a right angle triangle with sides of length ...