cosx/2 cosx/4 ……cosx/(2^n) =[cosx/2 cosx/4 ……cosx/(2^n) sinx/(2^n) ]/sinx/(2^n) =[cosx/2 cosx/4 ……cosx/(2^n-1) sinx/(2^n-1) ]/2sin/sinx/(2^n) =sinx/2^nsinx/(2^n) =sinx/sinx/(2^n)/(1/2^n) 当n趋向...