The integral is not all that difficult really but it does involve a fair number of steps to get it right. Here is a graph of what is being attempted:
I used symbolab to work through the solution which turns out to be:19(√3π−ln(8))
The first step in the solution is to factorise the denominator. This is easy because x3+1 is a sum of two cubes and so can be written as (x+1)(x2−x+1). Using partial fractions, the integral can be converted into the following form:131∫0x+1x2−x+1dx−131∫01x+1dx
The RHS integral is straightforward but the LHS one poses more difficulties. The way forward with the former is to write the quadratic in the denominator as a sum of two squares:131∫0x+1(x−12)2+34dx
This newly changed denominator can then be divided into the two parts of the numerator to yield:131∫0x(x−12)2+34+131∫01(x−12)2+34
I'm not going to go into the details here but, with the appropriate substitutions, the LHS of this integral can be integrated to a logarithm and the RHS to an arctan using the formulae:∫2tt2+1dt=ln|t2+1|+C and ∫1t2+1dt=tan−1t+C
The indefinite integral for x/(x3+1) turns out to be: 16(ln|4x2−4x+4|+2√3tan−1(2√3(x−12)))−13ln|x+1|+C
The definite integral for the limits of 0 and 1 is what was quoted earlier at the beginning of this post. In conclusion, I must say that Blogger is still inconsistently handling the display mode for LaTeX: sometimes it renders the LaTeX using the Javascript and other times it returns an image of the rendered code. Annoying.
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