=∫(0,π/4)(cosx-sinx)dx+∫(π/4,π/2)(sinx-cosx)dx知道答案是2(√2-1)但是忘了怎么算出来的了 囧

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=∫(0,π/4)(cosx-sinx)dx+∫(π/4,π/2)(sinx-cosx)dx知道答案是2(√2-1)但是忘了怎么算出来的了囧=∫(0,π/4)(cosx-sinx)dx+∫(π/4,π

=∫(0,π/4)(cosx-sinx)dx+∫(π/4,π/2)(sinx-cosx)dx知道答案是2(√2-1)但是忘了怎么算出来的了 囧
=∫(0,π/4)(cosx-sinx)dx+∫(π/4,π/2)(sinx-cosx)dx
知道答案是2(√2-1)但是忘了怎么算出来的了 囧

=∫(0,π/4)(cosx-sinx)dx+∫(π/4,π/2)(sinx-cosx)dx知道答案是2(√2-1)但是忘了怎么算出来的了 囧
∫(0,π/4)(cosx-sinx)dx
=sinx+cosx|(上π/4下0)
=√2-1
∫(π/4,π/2)(sinx-cosx)dx
=-sinx-cosx|(上π/2下π/4)
=-1+√2
两部分相加,得2(√2-1)

∫(0,π/4)(cosx-sinx)dx+∫(π/4,π/2)(sinx-cosx)dx
=sinx+cosx (0,π/4) +(-cosx-sinx) (π/4,π/2)
=√2-1+(-1+√2)
=2√2-2
=2(√2-1)