如题所述
[x^2sin(1/x)]'=(x^2)'sin(1/x)+(x^2)[sin(1/x)]'
=2xsin(1/x)+(x^2)[cos(1/x)](1/x)'=2xsin(1/x)+(x^2)[cos(1/x)](-1/x^2)
2xsin(1/x)-cos(1/x)ã
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