Please help!

01x4+1x6+1dx=π3\int_{0}^{1}\dfrac{x^4+1}{x^6+1}dx=\dfrac{\pi}{3}.Please prove the above statement.

#Integration #DefiniteIntegral

Note by Adarsh Kumar
5 years, 10 months ago

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Comments

01x4+1x6+1=01x4+1(x2+1)(x4x2+1) \int_0^1 \dfrac{x^4+1}{x^6+1} = \int_0^1 \dfrac{x^4+1}{(x^2+1)(x^4 - x^2 + 1)}

=01x4x2+1(x2+1)(x4x2+1)+01x2(x2+1)(x4x2+1)= \int_0^1 \dfrac{x^4-x^2+1}{(x^2+1)(x^4 - x^2 + 1)} + \int_0^1 \dfrac{x^2}{(x^2+1)(x^4 - x^2 + 1)}

=011x2+1+01x2x6+1 = \int_0^1 \dfrac{1}{x^2+1} + \int_0^1 \dfrac{x^2}{x^6+1}


With 01x2x6+1dx\displaystyle \int_0^1 \dfrac{x^2}{x^6+1} dx , substitute x3=u 3x2 dx=dux^3 = u \Rightarrow \ 3x^2 \ dx = du to make it as 01du3(u2+1)\displaystyle \int_0^1 \dfrac{du}{3(u^2+1)} .

The rest must be a baby's play for you I guess!

Satyajit Mohanty - 5 years, 10 months ago

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Nice solution !

Rajdeep Dhingra - 5 years, 10 months ago

Many thanks,bhaiya.I am grateful.

Adarsh Kumar - 5 years, 10 months ago

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Well, while integrating Rational Functions of the form P(x)Q(x)\dfrac{P(x)}{Q(x)}, my first strategy is always to compare the degrees of P(x)P(x) and Q(x)Q(x). If deg(P(x))<deg(Q(x))deg(P(x)) < deg(Q(x)), I always invoke partial fractions. If deg(P(x))>deg(Q(x)deg(P(x)) > deg(Q(x) , turn it into the form P(x)Q(x)=R(x)+S(x)Q(x)\dfrac{P(x)}{Q(x)} = R(x) + \dfrac{S(x)}{Q(x)} where deg(S(x))<deg(Q(x))deg(S(x)) < deg(Q(x)), and then I invoke partial fractions!

Satyajit Mohanty - 5 years, 10 months ago

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@Satyajit Mohanty A lot of problems can be cracked by this statergy :)

Satyajit Mohanty - 5 years, 10 months ago
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