Chapter 13 - Conic Sections - 13.1 Conic Sections: Parabolas and Circles - 13.1 Exercise Set - Page 854: 33

$x^2+y^2=64$

Using $(x-h)^2+(y-k)^2=r^2$ or the Center-Radius form of the equation of circles, the equation of the circle with center, $( 0,0 ),$ and radius, $r= 8 ,$ is \begin{array}{l}\require{cancel} (x-0)^2+(y-0)^2=8^2 \\\\ x^2+y^2=64 .\end{array}