∫ln(x^2+1)dx,怎么算
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∫ln(x^2+1)dx,怎么算
![∫ln(x^2+1)dx,怎么算](/uploads/image/z/1465955-35-5.jpg?t=%E2%88%ABln%28x%5E2%2B1%29dx%2C%E6%80%8E%E4%B9%88%E7%AE%97)
分部积分
∫ln(x^2+1)dx = ∫x d ln(x^2+1) = xln(x^2+1) - ∫x d ln(x^2+1)
= xln(x^2+1) - 2∫(x^2/x^2+1)dx
= xln(x^2+1) - 2∫(x^2+1-1)/(x^2+1)dx
= xln(x^2+1) - 2[∫(x^2+1)/(x^2+1)dx -∫(1/x^2+1)dx]
= xln(x^2+1) - 2[∫dx -∫(1/x^2+1)dx]
= xln(x^2+1) - 2[x - arctanx]+C
∫ln(x^2+1)dx = ∫x d ln(x^2+1) = xln(x^2+1) - ∫x d ln(x^2+1)
= xln(x^2+1) - 2∫(x^2/x^2+1)dx
= xln(x^2+1) - 2∫(x^2+1-1)/(x^2+1)dx
= xln(x^2+1) - 2[∫(x^2+1)/(x^2+1)dx -∫(1/x^2+1)dx]
= xln(x^2+1) - 2[∫dx -∫(1/x^2+1)dx]
= xln(x^2+1) - 2[x - arctanx]+C