Question 169976
If the diameter is 8.2, then the radius is simply half the diameter. So the radius is {{{r=8.2/2=4.1}}}



Since the center is (4,5), this means that h=4 and k=5. Note: remember, the center of any circle is (h,k)


{{{(x-h)^2+(y-k)^2=r^2}}} Start with the general equation of a circle



{{{(x-4)^2+(y-5)^2=(4.1)^2}}} Plug in {{{h=4}}}, {{{k=5}}} (this is the center) and {{{r=4.1}}}



{{{(x-4)^2+(y-5)^2=16.81}}} Square 4.1 to get 16.81



So the equation of the circle with a center of (4,5) and a diameter of 8.2 units is {{{(x-4)^2+(y-5)^2=16.81}}}