Describe the 3-space graph of the equation z
2 = y
2 + x
2.
◦ a surface of revolution obtained by rotating the parabola z = y
2 in the yz-plane about the z-axis
◦ a surface of revolution obtained by rotating the parabola z = x
2 in the xz-plane about the z-axis
◦ a circle having radius z in the xy-plane
◦ a circular cone with vertex at the origin, axis along the z-axis, and semi-vertical angle
◦ a circular cylinder with axis along the z-axis radius z