The graph of is an infinitely long cylinder whose central axis is the
A) line x = z
B) line x = y
C) x-axis
D) y-axis
E) z-axis

Question

The graph of  is an infinitely long cylinder whose central axis is the
A) line x = z 
B) line x = y 
C) x-axis 
D) y-axis 
E) z-axis

Quizplus · Accepted Answer

The equation x^2 + y^2 = 1 describes a circle in the plane perpendicular to the z-axis. When this circle is "revolved" about the z-axis, we obtain an infinitely long cylinder. The z-axis is the axis of symmetry for this cylinder, and therefore the answer is choice E.

The Graph of Is an Infinitely Long Cylinder Whose