How to Graph r=2cos(theta) in Cylindrical Coordinates?

[ranger1716]

I'm having some trouble understanding exactly how to graph this problem using cylindrical coordinates. The coordinates they give me is r=2cos(theta)

How do I go about beginning to determine how to graph this with only the radius?

 

[0rthodontist]

Anywhere the angle is pi/3, r = 1, no matter what z is--the horizontal cross section is the same as you move up or down. The set of points satisfying that equation is therefore a set of vertical lines. To find the cross section (in a form that you can recognize) you could start by converting the equation to rectangular coordinates.