arccos vs arc cosine

arccos and arc cosine both are nouns.

Word	Noun	Adjective	Verb	Adverb
arccos	Yes	No	No	No
arc cosine	Yes	No	No	No

As nouns, arccos and arc cosine are synonyms defined as:

arccos and arc cosine: the inverse function of the cosine; the angle that has a cosine equal to a given number

Other synonyms of arccos include arccosine, inverse cosine.

arccos (noun)	arc cosine (noun)
the inverse function of the cosine; the angle that has a cosine equal to a given number	the inverse function of the cosine; the angle that has a cosine equal to a given number