cos1的极限,

lim cos(根号下(n 1-根号n,n趋向无穷 这个式子怎么算呢
(1 sin2x(1-cos4x)的极限,x/4
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1-cos(xy(x^2 y^2)的极限,求过程
lim(1-cosx/x^2(x趋于0)求极限.