Giải các pt sau :
1) $\frac{2\sqrt{3}cos^{3}2x+2sin^{3}2x}{\sqrt{3}cos2x-sin2x}=cos4x$
2)$\frac{40(sin^{3\frac{x}{2}}-cos^{3}\frac{x}{2})}{16sin\frac{x}{2}-25sin\frac{x}{2}}=sinx$
3) $\frac{1}{sinx}-\frac{1}{sin2x}= \frac{1}{sin4x}$
4) $\frac{1-sin^{6}-cos^{6}x}{1-sin^{4}x-cos^{4}x}=2cos^{2}3x$
