【求教几道高数题,有关微积分∫(π,0)(xsinx)^2d-查字典问答网
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  【求教几道高数题,有关微积分∫(π,0)(xsinx)^2dx(积分符号的括号里左边是积分上限,右边是积分下限,下同)∫(2,0)xdx/(x^4-2x+2)^2设F(x)=∫(x,0)sint*dt/t,求F'(0).∫(3x^4+2x^2)dx/(x^2+】

  求教几道高数题,有关微积分

  ∫(π,0)(xsinx)^2dx (积分符号的括号里左边是积分上限,右边是积分下限,下同)

  ∫(2,0)xdx/(x^4-2x+2)^2

  设F(x)=∫(x,0)sint*dt/t,求F'(0).

  ∫(3x^4+2x^2)dx/(x^2+1)

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2020-06-24 11:32
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谭明皓

  (1)∫[0,π](xsinx)^2dx

  =1/2∫[0,π]x^2(1-cos2x)dx

  =1/2∫[0,π]x^2dx-1/4∫[0,π]x^2dsin2x

  =1/6x^3|[0,π]-1/4x^2sin2x|[0,π]+1/2∫[0,π]xsin2xdx

  =π^3/6-1/4∫[0,π]xdcos2x

  =π^3/6-1/4xcos2x|[0,π]+1/4∫cos2xdx

  =π^3/6-π/4+1/8sin2x|[0,π]

  =π^3/6-π/4

  (2)∫[0,2]xdx/(x^2-2x+2)^2(疑错,已改)

  =∫[0,2][(x-1)+1]dx/(x^2-2x+2)^2

  =-1/2*1/(x^2-2x+2)|[0,2]+∫[0,2]d(x-1)/[(x-1)^2+1]^2

  =1/2*(x-1)/[(x-1)^2+1]|[0,2]+1/2arctan(x-1)|[0,2]

  =1/4+1/4+π/8+π/8

  =1/2+π/4

  (3)F(x)=∫[0,x]sintdt/t

  F'(x)=sinx/x

  F'(0)=lim[x-->0]sinx/x=1

  (4)∫(3x^4+2x^2)dx/(x^2+1)

  =∫[3x^2-1+1/(x^2+1)]dx

  =x^3-x+arctanx+C

2020-06-24 11:34:54

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