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lim根号下(1-cosx平方)/(1-cosx)=

来源:学生作业帮 编辑:作业帮 分类:数学作业 时间:2024/05/03 07:58:35
lim根号下(1-cosx平方)/(1-cosx)=
是cos(x*x),不是cosx*cosx
lim(x->0)[√(1-cos(x²))/(1-cosx)]
=lim(x->0)[√(2sin²(x²/2))/(2sin²(x/2))] (应用三角函数倍角公式)
=lim(x->0)[√2sin(x²/2)/(2sin²(x/2))]
=lim(x->0)[√2*(sin(x²/2)/(x²/2))*((x/2)/sin(x/2))²]
=√2*lim(x->0)[sin(x²/2)/(x²/2)]*lim(x->0)[(x/2)/sin(x/2)]
=√2*1*1 (应用重要极限lim(t->0)(sint/t)=1)
=√2.