What is [math]\displaystyle\lim_{x\to 0}\frac{x-\tan x }{x-\sin x }[/math]? Why does [math]\displaystyle\lim_{x\to 0}\frac{\sin(x)}{x}=1[/math] but [math]\displaystyle\lim_{x\to 0}\frac{\sin(\frac{1}{x})}{\frac{1}{x}}=0[/math]?