Write the set of values of a for which f(x) = cosx + a2x + b is strictly increasing on R.

f(x) = Cos x + a2x + b


f’(x) = -Sin x + a2 + 0


f’(x) = a2 - Sin x


f(x) is strictly increasing on R


f’(x) > 0, x ϵ R


a2 – Sin x > 0, x ϵ R


a2 > Sin x, x ϵ R


Maximum value of Sin x is 1.


a2 > Sin x, a2 is always greater than 1.


a2 > 1


a2 – 1 > 0


(a + 1) (a – 1) > 0


a ϵ (-∞, -1) (1, ∞)


1