Equation Of A Circle

In this video we discover the equation of a circle, thanks to how it looks on a graph. The equation of a circle is (x - a)^2 + (y - b)^2 = r^2, where (a, b) is the centre of the circle and r is the radius. The coordinates of the centre point (a, b) are in the brackets with the x and y, but you just need to remember to change the sign of (a, b). We will look at how to find the equation of a tangent to a circle in another video.