How do you find the exact value of #arccos(cos((5π)/4))#?
If y = arc cos(x), cos(x) is single-valued.
Yet, y is many-valued in the form
If the range for y is specified, we have to pick value(s) from the general formula and give the answer.
This question does not arise at all, when we apply, in succession, an operator and its inverse, on an operand. The result is the operand.
In the other way about,