adobe illustrator - Drawing a line segment (or an arc) with an arrow head placed somewhere between the endpoints

I am trying to draw a line (or an arc) in Adobe Illustrator that looks something like this:

(Picture taken from Allen Hatcher's ``Notes on Introductory Point-Set Topology,'' pp. 22.)

My problem is that I can't place the arrowhead exactly halfway on the curve between the endpoints, or on any point on the curve.

Can anyone please help me?

Answer

Step1: Create 4 circles

Step 2: remove unwanted arcs (joining strokes is not necessary, but optional if you want to play around with anchors)

Step 3: Copy top 2 arcs into new layer (when pasting, use cnrl+shift+alt+v to paste in exacly same place) and add arrow ends

Step 4: Show both layers (note - otherwise, have undesirable stroke endings meeting arrowheads)

Step 5: Add circles & letters

Note: If for math publication, you might want to create using TEX as opposed to Illustrator (there is a good Tex SE) for more professional finish/ proper mathematical fonts, etc