ar- vs arc-

ar-

prefix
  • Used to form the names of inverse hyperbolic trigonometric functions, and the symbols for these functions. 

  • Forming classification names for classes of organic compounds that contain a carbon skeleton and one or more aromatic rings. 

arc-

prefix
  • Used to form the names of inverse trigonometric functions, and the symbols for these functions. 

How often have the words ar- and arc- occurred in a corpus of books? (source: Google Ngram Viewer )