原式=∫[∫[-π/2,π/2][cosxdx/(1+(cosx)^2]+∫[-π/2,π/2][xcosxdx/(1+(cosx)^2]
前一项是偶函数,后一项是奇函数,积分为0,
原式=2∫[0,π/2][cosxdx/(1+(cosx)^2]
=2∫[0,π/2]dsinx/[2-(sinx)^2]
设t=sinx,
原式=2∫[0,1]]dt/(2-t^2)
=2*/(2√2)ln|√2-t|/|√2+t|[0,1]
=(√2/2)ln(3+2√2).
原式=∫[∫[-π/2,π/2][cosxdx/(1+(cosx)^2]+∫[-π/2,π/2][xcosxdx/(1+(cosx)^2]
前一项是偶函数,后一项是奇函数,积分为0,
原式=2∫[0,π/2][cosxdx/(1+(cosx)^2]
=2∫[0,π/2]dsinx/[2-(sinx)^2]
设t=sinx,
原式=2∫[0,1]]dt/(2-t^2)
=2*/(2√2)ln|√2-t|/|√2+t|[0,1]
=(√2/2)ln(3+2√2).