计算:定积分∫(在上 √3,在下0 )xarctan

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计算:定积分∫(在上 √3,在下0 )xarctan
计算:定积分∫(在上 √3,在下0 )xarctan

计算:定积分∫(在上 √3,在下0 )xarctan
∫[0,√3]xarctan xdx
=1/2∫[0,√3]arctan xdx^2
=1/2x^2arctanx[0,√3]-1/2∫[0,√3]x^2darctan x
=π/2-1/2∫[0,√3]x^2/(1+x^2)dx
=π/2-1/2∫[0,√3][1-1/(1+x^2)]dx
=π/2-1/2(x-arctanx)[0,√3]
=π/2-√3/2+π/6
=2π/3-√3/2

∫(在上 √3,在下0 )xarctan xdx
=∫(在上 √3,在下0 )arctan xdx²/2
=x²/2arctanx|(0->√3)-1/2∫(0->√3)x²/(1+x²)dx
=π/2 -1/2 ∫(0->√3)(1-1/(1+x²))dx
=π/2-√3/2+1/2arctanx|(0->√3)
=π/2-√3/2+π/6
=2π/3-√3/2

令 t=arctan x, x=tan t ,dx=dtan t,原式=