∫1/(x^4+1)^2 dx 怎么求?
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原式=∫1/(x^4+2x^2+1-2x^2)^2dx
=∫1/[(x^2+1)^2-2x^2]^2dx
=∫1/[(x^2+√2x+1)(x^2-√2x+1)]dx
=(1/16)*∫[(3√2x+6)/(x^2+√2x+1)+(2√2x+2)/(x^2+√2x+1)^2-(3√2x-6)/(x^2-√2x+1)-(2√2x-2)/(x^2-√2x+1)^2]dx
=[3√2*(x^4+1)*ln(x^2+√2x+1)-3√2*(x^4+1)*ln(x^2-√2x+1)+6√2*(x^4+1)*arctan(√2x+1)+6√2*(x^4+1)*arctan(√2x-1)+8x]/32(x^4+1)
=(3√2/32)*[ln(x^2+√2x+1)-ln(x^2-√2x+1)]+(3√2/16)*[arctan(√2x+1)+arctan(√2x-1)]+x/4(x^4+1)+C,其中C是任意常数
=∫1/[(x^2+1)^2-2x^2]^2dx
=∫1/[(x^2+√2x+1)(x^2-√2x+1)]dx
=(1/16)*∫[(3√2x+6)/(x^2+√2x+1)+(2√2x+2)/(x^2+√2x+1)^2-(3√2x-6)/(x^2-√2x+1)-(2√2x-2)/(x^2-√2x+1)^2]dx
=[3√2*(x^4+1)*ln(x^2+√2x+1)-3√2*(x^4+1)*ln(x^2-√2x+1)+6√2*(x^4+1)*arctan(√2x+1)+6√2*(x^4+1)*arctan(√2x-1)+8x]/32(x^4+1)
=(3√2/32)*[ln(x^2+√2x+1)-ln(x^2-√2x+1)]+(3√2/16)*[arctan(√2x+1)+arctan(√2x-1)]+x/4(x^4+1)+C,其中C是任意常数
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