6.3. Find all solutions of the inequality

$$
\sin ^{2018} x+\cos ^{-2019} x \leqslant \cos ^{2018} x+\sin ^{-2019} x
$$

belonging to the interval $\left[-\frac{5 \pi}{4} ; \frac{3 \pi}{4}\right]$.
Answer: $\left[-\frac{5 \pi}{4} ;-\pi\right) \cup\left[-\frac{3 \pi}{4} ;-\frac{\pi}{2}\right) \cup\left(0 ; \frac{\pi}{4}\right] \cup\left(\frac{\pi}{2} ; \frac{3 \pi}{4}\right]$.