Lead to the algebraic form of Arccos(pi) and Arth(4)

[Resistor]

\(\displaystyle \mbox{6) Arccos}\, \pi\). . . .\(\displaystyle \mbox{B) Arth}\, 4\)

Hello everyone, hope for your help, and sorry for my english.
Firsly, I guess Arth is an hyperbolic arctan, isnt it?
And these numbers are obviously complex, but I need it in algebraic form.
Whats the way to do it? Should I use a complex-value function?

 

[Otis]

\(\displaystyle \mbox{6) Arccos}\, \pi\). . . .\(\displaystyle \mbox{B) Arth}\, 4\)

I guess Arth [means] hyperbolic arctan

... I need it in algebraic form.

arctanh(z) = Arth(z) = 1/2*[ln(1 + z) - ln(1 - z)]