Pseudo-elliptic integrals

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Integrals ∫f(x,y) dx\int f(x,y)\, dx, where f(x,y)f(x,y) is a rational function and y=Ax4+Bx3+Cx2+Dx+Ey=\sqrt{Ax^{4}+Bx^{3}+Cx^{2}+Dx+E}, called elliptic integrals, generally cannot be integrated in closed form unless there are special relations among the coefficients of the function f(x,y)f(x,y) or of the polynomial Ax4+Bx3+Cx2+Dx+EAx^{4}+Bx^{3}+Cx^{2}+Dx+E.

In the following examples with palindromic polynomials, one of the substitutions x+1x=ux+\frac{1}{x}=u or x−1x=vx-\frac{1}{x}=v makes it comparatively easy to obtain the integral. Find the integral ∫x2−1x2+1dxx4+1\int \frac{x^{2}-1}{x^{2}+1}\frac{dx}{\sqrt{x^{4}+1}}.

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Find the integral ∫x2+1x2−1dxx4+1\int \frac{x^{2}+1}{x^{2}-1}\frac{dx}{\sqrt{x^{4}+1}}.

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Find the integral ∫x2−1x1+3x2+x4 dx\int \frac{x^{2}-1}{x\sqrt{1+3x^{2}+x^{4}}}\, dx.

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Find the integral ∫(x2+1) dxxx4+3x3−2x2−3x+1\int \frac{(x^{2}+1)\, dx}{x\sqrt{x^{4}+3x^{3}-2x^{2}-3x+1}}.

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Find the integral ∫1+x41−x4 dx\int \frac{\sqrt{1+x^{4}}}{1-x^{4}}\, dx.

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Find the integral ∫x+1x−1dxx(x2+x+1)\int \frac{x+1}{x-1}\frac{dx}{\sqrt{x(x^{2}+x+1)}}.

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Find the integral ∫x+1x−2dx1+x3\int \frac{x+1}{x-2}\frac{dx}{\sqrt{1+x^{3}}}.

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Find the integral ∫(x2−a2) dxxa4+x4\int \frac{(x^{2}-a^{2})\, dx}{x\sqrt{a^{4}+x^{4}}}.

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Find the integral ∫dx(1+x4)1+x4−x2\int \frac{dx}{(1+x^{4})\sqrt{\sqrt{1+x^{4}}-x^{2}}}.

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Find the integral ∫dx(x−2)(2−3x+x3)\int \frac{dx}{\sqrt{(x-2)(2-3x+x^{3})}}.

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Find the pseudo-elliptic integral:

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(1)

∫dxx7x4+1\int \frac{d x}{x^{7} \sqrt{x^{4}+1}}

(2)

∫(x2−1) dx(x2+1)x4+1\int \frac{\left(x^{2}-1\right) \, d x}{\left(x^{2}+1\right) \sqrt{x^{4}+1}}

(3)

∫(x−1) dx(x+1)x3+x2+x\int \frac{(x-1) \, d x}{(x+1) \sqrt{x^{3}+x^{2}+x}};

(4)

∫(x2+1)dxxx4+3x3−2x2−3x+1,x>1\int \frac{\left(x^{2}+1\right) d x}{x \sqrt{x^{4}+3 x^{3}-2 x^{2}-3 x+1}}, x > 1.

References

[ГюКу03] Гюнтер Н.М., Кузьмин Р.О. Сборник задач по высшей математике. 13-е изд., Издательство «Лань», 2003.
[ККЧ+03] Кудрявцев Л.Д., Кутасов А.Д., Чехлов В.И., Шабунин М.И. Интегралы. Ряды. 2-е изд., ФИЗМАТЛИТ, 2003.