MathematicsEasy175×since 2002Q2706Let f(x) = sin⁴x + cos⁴ x. Then f is an increasing function in the interval :A]0,π4[] 0, \frac{\pi}{4}[]0,4π[B]π4,π2[] \frac{\pi}{4}, \frac{\pi}{2}[]4π,2π[C]π2,5π8[] \frac{\pi}{2}, \frac{5 \pi}{8}[]2π,85π[D]5π8,3π4[] \frac{5 \pi}{8}, \frac{3 \pi}{4}[]85π,43π[Check answerSkip