x (float or np.ndarray or Tensor or Pwc or Stf) – The object whose arccosine you want to calculate, \(x\). Must be real. For numbers,
arrays, and tensors, the object is converted to a tensor and then the operation is applied.
For functions of time (Pwcs and Stfs), the composition of the operation with the
function is computed (that is, the operation is applied to the function values).