Let the function `f:R to R` be defined by `f(x)=cos x, AA x in R.` Show that `f` is neither one-one nor onto.

Explanation

To show that the function \( f: \mathbb{R} \to \mathbb{R} \) defined by \( f(x) = \cos x \) is neither one-one nor onto, we will analyze both properties step by step.

### Step 1: Check if the function is one-one (injective)

1. **Assume \( f(x_1) = f(x_2) \)**:
\[ \cos x_1 = \cos x_2 \]
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