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
