Horizontal Line Test

A function is one-to-one if every horizontal line meets its graph at most once.

Determine whether the following functions are one-one:

1. \(\mathrm{f} (x) = |x - 1| ; x \in \mathbb{R}\)
2. \(\mathrm{g} (x) = 2(x + 2)^{3} ; x \in \mathbb{R}\)
3. \( \mathrm{h} (x) = \cos x, ; x \in \mathbb{R} ; 0 \le x \le \pi\)