Question

Find the range of the function f(x) = sin(log(5x² – 8x + 4)) 

Answer 1

Clearly, 5x² - 8x + 4 > 0, ∀ x ∈ R

Also, 5x² - 8x + 4 = 5(x - 4/5)² + 4/5

Thus, the range of log (5x² – 8x + 4) is

= (log(4/5), ∞)

Hence, R_f = [-1, 1]