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问题: 计算:lim[(CosA^n+SinA^n)/(SinA^n-CosA^n)] (π/4
计算:lim[(CosA^n+SinA^n)/(SinA^n-CosA^n)] (π/4<A<π/2)

解答:

解:因为π/4<A<π/2,所以0<CosA<SinA
lim[(CosA^n+SinA^n)/(SinA^n-CosA^n)](分子分母都除以SinA^n)
=lim[(CosA^n/SinA^n+1)/(1-CosA^n/SinA^n)]
=lim[(CotA^n+1)/(1-CotA^n)](0<CotA<1)
=(0+1)/(1-0)=1