Tuesday, 20 November 2018

integration - Integrating intfracpi20fracxcos(x)+sin(x)mathrmdx using complex analysis

I am struggling with the integration of I=π20xcos(x)+sin(x)dx

using complex analysis. I used the substitution z=eixdx=1izdz and hence cos(x)+sin(x)=((z+1z)i(z1z)) because we have cos(x)=12(eix+eix), and sin(x)=12i(eixeix), and x=iln(z). However I am not successful to obtain the correct result when using real analysis, which gives I=π20xsinx+cosxdx=0.978959918



Any idea how to calculate this integral using complex analysis and Cauchy integral theorem?

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