sinx+sin3x+sin5x+.sin(2n-1)/cosx+cos3x+cos5x+.cos(2n-1)= sin
sinx+sin3x+sin5x+.sin(2n-1)/cosx+cos3x+cos5x+.cos(2n-1)= sin2x+sin4x+.sin 2nx /cos2x
sinx+sin3x+sin5x+.sin(2n-1)/cosx+cos3x+cos5x+.cos(2n-1)=
sin2x+sin4x+.sin 2nx /cos2x+cos4x+.cos2nx =
已知数列an通项公式(n+2)*(9/10)的n次方,求n为何值an最大,并求最大值