Determine whether the following functions are one-to-one or not.

? Yes No 1. Is the function $f(x) = x^{2}+2x$ one-to-one?

? Yes No 2. Is the function $g(x) = \cos\!\left(x\right)$ one-to-one?

? Yes No 3. Is the function $h(x) = \displaystyle \frac{1}{x}$ one-to-one?