[napong]

$\sqrt{sin^{4}(x)+4cos^2(x)}$-$\sqrt{cos^4(x)+4sin^2(x)}$ = ($\sqrt{2}$cos$\frac{5\Pi }{14}$-$\frac{1}{\sqrt{2} }$ )($\sqrt{2}$cos$\frac{15\Pi }{14}$-$\frac{1}{\sqrt{2} }$ )($\sqrt{2}$cos$\frac{45\Pi }{14}$-$\frac{1}{\sqrt{2} }$ )
หา tan(x)