lim(x→0) (1/sin^2 x-1/x^2 cos^2 x)=? "limx趋向于0.(sin方x)分之一,...lim(x→0) (1/sin^2 x-1/x^2 cos^2 x)=?"limx趋向于0.(sin方x)分之一,减,(x方乘以cos方x)分之一"请写明过程.我只知道最后答案是

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lim(x→0) (1/sin^2 x-1/x^2 cos^2 x)=? "limx趋向于0.(sin方x)分之一,...lim(x→0) (1/sin^2 x-1/x^2 cos^2 x)=?"limx趋向于0.(sin方x)分之一,减,(x方乘以cos方x)分之一"请写明过程.我只知道最后答案是
lim(x→0) (1/sin^2 x-1/x^2 cos^2 x)=? "limx趋向于0.(sin方x)分之一,...
lim(x→0) (1/sin^2 x-1/x^2 cos^2 x)=?
"limx趋向于0.(sin方x)分之一,减,(x方乘以cos方x)分之一"
请写明过程.
我只知道最后答案是 -2/3

lim(x→0) (1/sin^2 x-1/x^2 cos^2 x)=? "limx趋向于0.(sin方x)分之一,...lim(x→0) (1/sin^2 x-1/x^2 cos^2 x)=?"limx趋向于0.(sin方x)分之一,减,(x方乘以cos方x)分之一"请写明过程.我只知道最后答案是
=lim (x²·cos²x - sin²x)/(sin²x·x²·cos²x)
=lim (x²·cos²x - sin²x)/(x²·x²·1)《等价无穷小代换》
=lim (x²·cos²x - sin²x) / x^4
=lim (2x·cos²x - 2x²·cosx·sinx - 2sinx·cosx) / (4x³) 《洛比达法则》
=lim (x·cosx - x²·sinx - sinx)·cosx / (2x³)
=lim (x·cosx - x²·sinx - sinx) / (2x³)
=lim [(cosx - x·sinx)- (2x·sinx + x²·cosx) - cosx] / (6x²) 《洛比达法则》
=lim (-3x·sinx - x²·cosx) / (6x²)
=lim -(3sinx + x·cosx) / (6x)
=lim -[3cosx + (cosx - x·sinx)] / 6 《洛比达法则》
=lim -(4cosx - x·sinx) / 6
= -(4×1 - 0) / 6
= -2/3

limx趋向于0。1/(sin方x)-1/(x方乘以cos方x)
=lim [(sin方x)-(x方乘以cos方x)]/[(sin方x)(x方乘以cos方x)]
=lim [sin²x-x²(1-sin²x)]/[sin²x*x²(1-sin²x)]
=lim [sin²x-x²+x²sin²x)]/[sin²x*x²-x²sin^4x]
=lim x^4/(x^4-x^6)
=1