The cylinder is a clue to use cylindrical coordinates. Taking

and

, we then are forced to use

. So the parameterization of the intersection of the plane and cylinder is

To get the surface, we can introduce a second parameter

that "contracts" the elliptical intersection to a point. The simplest way to do this is to use

with

and

.
Answer:
-1/2
Step-by-step explanation:
cos(x+pi) = -cos(x), so the answer is -1/2.