$$$\operatorname{acos}{\left(1 \right)}$$$
The calculator will find the inverse cosine of $$$1$$$ in degrees and radians.
Related calculator: Inverse Cosine Calculator
Answer
$$$\operatorname{acos}{\left(1 \right)} = 0$$$A
$$$\operatorname{acos}{\left(1 \right)} = 0^{\circ}$$$A
For graph, see the graphing calculator.