 So now we have come to the standard equation of a circle and this is what you're going to want to write down in your notes x minus h squared plus y minus k squared equals r squared. This is the standard equation of a circle that is derived from the distance formula and we want to note a couple of things here. It is similar to the distance formula that if we find this distance r the distance formula says we're going to find the difference of the x values and then find the difference of the y values. The center of the circle here is represented in the standard equation of a circle by the letters h and k. So don't get thrown by the letters there, just remember that these values right here represent the center of the circle and you're going to find the opposite signs of those. We'll practice those in the next couple of videos. And then r of course just represents our radius. And then you can write down in your notes the definition of a circle officially is all points in a plane that are equidistant from the center point and that makes sense. Any point on this circle is going to be a distance of r from the center point. And so this video you should just be able to recognize when you see an equation in this form that it's going to represent a circle.