We want to calculate the integral of the function x*sin(x^4), from 0 to infinity.
We may think that this is similar to a Fresnel Integral (sin(x^2)). In that case, we would set z=e^(iz)^2, and then integrate over the special contour with regions I: 0 to R, II: theta = 0 to pi/4 and then finally to region III: R to 0 along e^i*pi/4. Now, this leads to the problem of integrating the function x*e^(i*x)^4.
A much simpler approach is suggested.© BrainMass Inc. brainmass.com March 5, 2021, 12:34 am ad1c9bdddf
The solution is the integral (with limits between 0 and infinity) of ...
We calculate the integral of the function x*sin(x^4), from 0 to infinity using the known value at infinity of the Fresnel integral of sin(x^2).