## Question

True or False?

The graph of x^2+y^2=1 in 3-space is a circle of radius 1 centered at the origin.

x^2+y^2=1 is a circle of radius centered at the origin in xy-plane.
But 3-space contains z and for each value of z, there is one such circle.
This means, that in 3-space x^2+y^2=1 is a cylinder.