f(x) = Sin x – ax + 4
f’(x) = Cos x – a + 0
f’(x) = Cos x – a
\(\because\) f(x) is increasing on R.
f’(x) > 0
\(\therefore\) Cos x – a > 0
Cos x > a
\(\because\) Cos x ≥ -1, ∀ x ∈ R
\(\therefore\) a < -1
\(\therefore\) a ∈ (-∞, -1)
Hence the required set of values is a ∈ (-∞, -1).
