Right angle △AHO 1 and FDH subtend angle ∠AHO 1=∠FHD.

Therefore ∠ ADF = ∠ ao1h.

Arc AF=GF Two semicircles have the same radius.

∠FPO 1=∠PO 1F

PF=O 1F=R=O2F

That is, P and O2 are the same point.