lim x趋于0 1-cosx^2/x^2sinX^2(1-cosx^2)/x^2sinx^2=[1-1-2sin^2(x^2/2)]/x^2sinx^2=2sin^2(x^2/2)/x^2sinx^2=(x->0)2(x^2/2)^2/x^2*x^2=1/2第二步是怎么来的?(1-cosx^2)/x^2sinx^2①=[1-1-2sin^2(x^2/2)]/x^2sinx^2②=2sin^2(x^2/2)/x^2sinx^2③=(x->0)2

来源:学生作业帮助网 编辑:作业帮 时间:2024/04/28 10:37:26

lim x趋于0 1-cosx^2/x^2sinX^2(1-cosx^2)/x^2sinx^2=[1-1-2sin^2(x^2/2)]/x^2sinx^2=2sin^2(x^2/2)/x^2sinx^2=(x->0)2(x^2/2)^2/x^2*x^2=1/2第二步是怎么来的?(1-cosx^2)/x^2sinx^2①=[1-1-2sin^2(x^2/2)]/x^2sinx^2②=2sin^2(x^2/2)/x^2sinx^2③=(x->0)2
lim x趋于0 1-cosx^2/x^2sinX^2
(1-cosx^2)/x^2sinx^2
=[1-1-2sin^2(x^2/2)]/x^2sinx^2
=2sin^2(x^2/2)/x^2sinx^2
=(x->0)2(x^2/2)^2/x^2*x^2=1/2
第二步是怎么来的?
(1-cosx^2)/x^2sinx^2①
=[1-1-2sin^2(x^2/2)]/x^2sinx^2②
=2sin^2(x^2/2)/x^2sinx^2③
=(x->0)2(x^2/2)^2/x^2*x^2=1/2④

lim x趋于0 1-cosx^2/x^2sinX^2(1-cosx^2)/x^2sinx^2=[1-1-2sin^2(x^2/2)]/x^2sinx^2=2sin^2(x^2/2)/x^2sinx^2=(x->0)2(x^2/2)^2/x^2*x^2=1/2第二步是怎么来的?(1-cosx^2)/x^2sinx^2①=[1-1-2sin^2(x^2/2)]/x^2sinx^2②=2sin^2(x^2/2)/x^2sinx^2③=(x->0)2
高中的公式:cos2A=1-2(sinA)^2.
令A=(x^2)/2,代入得:cosx^2=1-2sin^2(x^2/2).
因此,第2步的第二个减号应改为加号.

这显然是零比零型,用两次洛必达法则就可以了。

第一个等号后面少了一个括号,应该是{1-[1-2sin^(x^2/2)]}

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