## University Calculus: Early Transcendentals (3rd Edition)

a) $x^2+y^2=4^2 ; z=0$ b) $y^2+z^2=4; x=0$ c) $x^2+z^2=4; y=0$
Definition: The equations of a circle having radius $r$ with center at origin and lying in the xy-plane, yz-plane and xz-plane are represented as: $x^2+y^2=r^2$ when z=0 , $y^2+z^2=r^2$ when x=0 and $x^2+z^2=r^2$ when y=0 Thus, we have: a) $x^2+y^2=4^2 ; z=0$ b) $y^2+z^2=4; x=0$ c) $x^2+z^2=4; y=0$