Let’s find the equation of a circle with
radius r = 7 and center (h,k) =(6,8).
By definition, an equation of the circle with center (h,k) and radius r is
This is called the standard form for the equation of the circle. Then, in our case, replacing the data we have, we should have:
so, we can conclude that the equation of the circle with center (6,8) and radius 7 is :