Disk

Started tracing the iron man chest image, using at the moment only the Ellipse Tool which is found under the Rectangle Tool which is default.

I created the circles to line up with the markings of the chest, to get them perfect and in line with the dick I found the center of the disk, this can be see as it will say "Center" when the cursor is in the center. Then I held down Shift and Alt and right clicked and dragged to create a circle, holding Shift and Alt makes the circle come out from where you click so the initial click is the center of the shape, and not so where the cursor moves is the corner of the shape. 

Below shows all the circles done, the image i copied in was in the "center" but appeared the image wasn't completely centered in its self, so I lined all the circles up with the left side so all the spacing was the same. 

Due to the image no lining up 100% I'll finish the left side parts which aren't full circles then copy and flip them onto the right side. 

I did 2 circles for this part of the image:

So that they would have perfectly curved and in keeping edges, I will cut and join the ends.