The domain of the function is the set of real numbers. The function displays unexpected behavior for input values between 0 and 50, where it returns negative values instead of positive values.

[CODE]:
Based on the experiments, we can approximate the behavior of the function with the following Python code:

```python
def f(x):
    if x < 0:
        return 0.6875375568153886
    elif x >= 0 and x < 50:
        return -5.899278111793663
    else:
        return 7.7
```

However, please note that this is just an approximation based on the observed behavior from the experiments.