$\displaystyle \lim_{x \to 0} \left(\frac{10}{9}\frac{sin \, 9x}{sin \, 10x}\right) \left(\frac{8}{7}\frac{sin \, 7x}{sin \, 8x}\right) \left(\frac{6}{5}\frac{sin \, 5x}{sin \, 6x}\right) \left(\frac{4}{3}\frac{sin \, 3x}{sin \, 4x}\right) \left(\frac{sin \, x}{sin \, 2x}\right) $ =