In the first section, you create an equation curve in a 2D sketch as part of a profile. You then use the profile to create a revolve feature.
Create a new 2D sketch on the YZ origin plane.
Start the Equation Curve command. 

Dimension the horizontal line. Accept the default value of 2 mm. 
Finish the Sketch.
Start the Revolve command. The profile is selected automatically. Use the longer line as the axis of revolution. 