Сравните!! помогите пожалуйста решить! ;)

Решите задачу:

$\ (\frac{9}{4})^{\sqrt{6}} \ \textgreater \ (\frac{4}{9})^{-2.5} \\\ (\frac{9}{4})^{\sqrt{6}} \ \textgreater \ (\frac{9}{4})^{2.5} \\ \sqrt{6} \ \textgreater \ 2.5\\ \sqrt{6} \ \textgreater \ \sqrt{6.25}$

$2) (8-3\sqrt{7})^{2.5} \ = \ (8+3\sqrt{7})^{-2.5}\\ 8-3\sqrt{7}\ =\ \frac{1}{8+3\sqrt{7}}\\ (8-3\sqrt{7})*(8+3\sqrt{7}) = 1\\ (8-3\sqrt{7})^{2.5} \ = \ (8+3\sqrt{7})^{-2.5}$

$3) (\frac{\pi}{5})^{cos(\frac{\pi}{8})} \ \textless \ (\frac{\pi}{5})^{cos(0.4)} \\ cos(\frac{\pi}{8}) \ \textgreater \ cos(0.4)\\ \frac{\pi}{8} \ \textless \ 0.4\\ \frac{10\pi}{80} \ \textless \ \frac{32}{80}\\$