The number of times the function $$f(x)=|\min(\sin x,\cos x)|$$ takes the value $0.8$ between $\frac{20 \pi}{3}$ and $\frac{43 \pi}{6}$ is :
$A)2,\quad$ $B) \text{more than}\, 2,\quad$ $C)0, \quad $ $D)1$
I can only translate the interval into $[\frac{4 \pi}{6},\frac{7 \pi}{6}]$ but here what should I check to get the given answer?
note this is a past competition problem so use of any graphing calculator is not allowed. Only high school methods are acceptable. Thank you!