Re: [考古] 86清大理工

[stillboy (joey)]

  x^2 +1      x^2+1   x^2    x^2+1
S _____ dx = S______  ____   ____  dx
  x^4 +1      x^4 +1  x^2+1  x^2

  x^2
S _____ d(x-1/x)
 x^2+1

   1
S_____    d(x - 1/x)
 1 + 1/x^2

   1
S______    d(x-1/x)
(x-1/x)^2 +2

    1
S______   d(u)  =(u/2) arctan(u/2) + C
 u^2 +2


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