Question

数学题求导？

Answer 1

(1)
x^3-2x
=-x^2.(1-x)+x^2-2x
=-x^2.(1-x)-x(1-x)-x
=-x^2.(1-x)-x(1-x)-(1-x) +1
y
= (x^3-2x)/(1-x)

=-x^2-x -1 + 1/(1-x)
y'=-2x -1 + 1/(1-x)^2
(2)
y=(x+cosx)/sinx

y'
= [sinx.(x+cosx)' -(x+cosx).(sinx)' ]/(sinx)^2
= [sinx.(1-sinx) -(x+cosx).cosx ]/(sinx)^2
=(-1+sinx -xcosx)/(sinx)^2
(5)
y
= e^x/(1+e^x)
=1 - 1/(1+e^x)
y'
=e^x/(1+e^x)^2

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