# arccosine

The inverse of the cosine function, usually abbreviated arccos. It is defined on the restricted domain $$[-1,1]$$, such that for any real number $$x \in [-1,1]$$, $$\arccos(x)=a$$ if and only if $$\cos(a)=x$$. The principal arcosine takes its values in the interval $$[0,\pi]$$.

Arccosine may also be abbreviated by acos or cos-1.