Question

Find the values of ‘a’ for which f(x) = sin x − ax + b is increasing on R.

Answer 1

f(x) = sin x − ax + b

f'(x) = cos x − a

For increasing function,

f'(x) > 0

∴ cos x − a > 0

cos x > a

−1 < cos x < 1

⇒ a < −1

∴ a ∈ [−∞, −1]