noun arc·co·sine \(ˌ)är(k)-ˈkō-ˌsīn\

Definition of arccosine

  1. :  the inverse function of the cosine <if y is the cosine of θ, then θ is the arccosine of y> —abbreviation arccos

Circa 1884

First Known Use of arccosine

circa 1884

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