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1x3+1dx\int \frac{1}{x^{3}+1} \, dx

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Q. 1x3+1dx\int \frac{1}{x^{3}+1} \, dx
  1. Simplify using partial fractions: Step 11: Simplify the integral using partial fractions.\newlineWe start by expressing the denominator as a sum of simpler fractions:\newlinex3+1x^3 + 1 can be factored as (x+1)(x2x+1)(x + 1)(x^2 - x + 1).\newlineNow, we set up the partial fractions:\newline1x3+1=Ax+1+Bx+Cx2x+1\frac{1}{x^3 + 1} = \frac{A}{x + 1} + \frac{Bx + C}{x^2 - x + 1}.
  2. Solve for A, B, C: Step 22: Solve for A, B, and C.\newlineMultiply through by x3+1x^3 + 1 to clear the denominators:\newline1=A(x2x+1)+(Bx+C)(x+1)1 = A(x^2 - x + 1) + (Bx + C)(x + 1).\newlineExpanding and equating coefficients, we get:\newline1=Ax2Ax+A+Bx2+Bx+Cx+C1 = Ax^2 - Ax + A + Bx^2 + Bx + Cx + C.\newlineEquating coefficients:\newlineFor x2x^2: A+B=0A + B = 0,\newlineFor xx: A+B+C=0-A + B + C = 0,\newlineFor constant: A+C=1A + C = 1.
  3. Solve system of equations: Step 33: Solve the system of equations.\newlineFrom A+B=0A + B = 0, we get B=AB = -A.\newlineSubstituting B=AB = -A into A+B+C=0-A + B + C = 0 gives AA+C=0-A - A + C = 0, so C=2AC = 2A.\newlineSubstituting C=2AC = 2A into A+C=1A + C = 1 gives A+2A=1A + 2A = 1, so A=13A = \frac{1}{3}.\newlineThen, B=AB = -A00, and B=AB = -A11.
  4. Write integral with coefficients: Step 44: Write the integral with the found coefficients.\newlineThe integral becomes:\newline\int(\(1/(x^33 + 11))\,dx = \int(\frac{11}{33})/(x + 11)\,dx + \int(\frac{1-1}{33x} + \frac{22}{33})/(x^22 - x + 11)\,dx.
  5. Integrate each term: Step 55: Integrate each term.\newlineFor 131x+1dx\int\frac{1}{3}\frac{1}{x + 1}\,dx, the integral is 13lnx+1\frac{1}{3}\ln|x + 1|.\newlineFor 13x+23x2x+1dx\int\frac{-\frac{1}{3}x + \frac{2}{3}}{x^2 - x + 1}\,dx, we need to complete the square in the denominator:\newlinex2x+1=(x12)2+34x^2 - x + 1 = (x - \frac{1}{2})^2 + \frac{3}{4}.\newlineThe integral becomes more complex and involves a substitution and possibly trigonometric integration.

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