We know that any function f: A→B is invertible if and only if it is bijective. Now, f: R → R, which is given by f(x) = cos(5x + 2) is neither in objective nor subjective. For −1 ≤ cos(5x + 2) ≤ 1, the range of f ≠ R. Therefore, f is not subjective. Also
Therefore, f is not injective. Thus, f is not invertible. For the existence of inverse of a function, the given function must be one-to-one and onto.
