Showing posts with label substitution method. Show all posts
Showing posts with label substitution method. Show all posts

Saturday, April 25, 2015

Hard and Intriguing Indefinite Integral Problem (Second Method)

On this blog post, I will show another intelligent way to tackle the problem(Hard and Intriguing Indefinite Integral Problem ) that to compute the following indefinite integral:

[MATH]\int \dfrac{(3x^{10}+2x^8-2)\sqrt[4]{x^{10}+x^8+1}}{x^6} \,dx[/MATH]

If we rewrite the integrand such that we have:

Putnam Definite Integral Hard Problem: Evaluate $\displaystyle\int_0^{\frac{\pi}{2}}\frac{dx}{1+(\tan x)^{\sqrt{2}}}$.

Another hard definite integral but it is not as bad as it looks. Let's first try the substitution method:

Attempt I:

We are given to evaluate:

[MATH]I=\int_0^{\pi/2}\frac{1}{1+\left(\tan(x)\right)^{\sqrt{2}}}\,dx[/MATH]

If we use the substitution:

[MATH]u=\frac{\pi}{2}-x[/MATH]