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int_(Gamma)(e^(2))/(z*(2^(2)+1))dz

Γe2z(22+1)dz \int_{\Gamma} \frac{e^{2}}{z \cdot\left(2^{2}+1\right)} d z

Full solution

Q. Γe2z(22+1)dz \int_{\Gamma} \frac{e^{2}}{z \cdot\left(2^{2}+1\right)} d z
  1. Simplify the integral: Let's start by simplifying the integral a bit, we have:\newlinee2z(z2+1)dz\int\frac{e^{2}}{z(z^{2}+1)}dz\newlineNotice that e2e^{2} is a constant and can be factored out of the integral.\newlineSo, we get:\newlinee21z(z2+1)dze^{2} \cdot \int\frac{1}{z(z^{2}+1)}dz
  2. Partial fraction decomposition: Now, let's do a partial fraction decomposition on 1z(z2+1)\frac{1}{z(z^{2}+1)}. We want to express 1z(z2+1)\frac{1}{z(z^{2}+1)} as Az+Bz+Cz2+1\frac{A}{z} + \frac{Bz+C}{z^{2}+1}. To find AA, BB, and CC, we multiply both sides by z(z2+1)z(z^{2}+1) and compare coefficients. 1=A(z2+1)+(Bz+C)z1 = A(z^{2}+1) + (Bz+C)z
  3. Find coefficients: Setting z=0z=0 to find AA gives us:\newline1=A(0+1)1 = A*(0+1)\newlineSo, A=1A = 1.
  4. Integrate term by term: Now we need to find BB and CC. We can plug in different values for zz or compare coefficients. Let's compare coefficients for the z2z^2, zz, and constant terms. For z2z^2 terms: 0=A+B0 = A + B For zz terms: 0=C0 = C For constant terms: 1=A1 = A We already know CC00, so CC11 and CC22.
  5. Substitute and integrate: Now we have our partial fraction decomposition:\newline1z(z2+1)=1zzz2+1\frac{1}{z(z^{2}+1)} = \frac{1}{z} - \frac{z}{z^{2}+1}\newlineSo the integral becomes:\newlinee2(1zzz2+1)dze^{2} \cdot \int(\frac{1}{z} - \frac{z}{z^{2}+1})dz
  6. Combine logarithms: Let's integrate term by term.\newlineThe integral of 1zdz\frac{1}{z} \, dz is lnz\ln|z|.\newlineThe integral of zz2+1dz-\frac{z}{z^{2}+1} \, dz is a bit trickier, but we can use a substitution.\newlineLet u=z2+1u = z^2 + 1, then du=2zdzdu = 2z \, dz.
  7. Final simplification: We substitute and get:\newlinezz2+1dz=121udu\int -\frac{z}{z^{2}+1} dz = -\frac{1}{2} \int \frac{1}{u} du\newlineWhich integrates to 12lnu-\frac{1}{2} \ln|u|.
  8. Final simplification: We substitute and get:\newlinezz2+1dz=121udu\int -\frac{z}{z^{2}+1} dz = -\frac{1}{2} \int \frac{1}{u} du\newlineWhich integrates to 12lnu-\frac{1}{2} \ln|u|.Now we substitute back for u to get the integral in terms of z.\newline12lnu-\frac{1}{2} \ln|u| becomes 12lnz2+1-\frac{1}{2} \ln|z^{2} + 1|.
  9. Final simplification: We substitute and get:\newlinezz2+1dz=121udu\int -\frac{z}{z^{2}+1} dz = -\frac{1}{2} \int \frac{1}{u} du\newlineWhich integrates to 12lnu-\frac{1}{2} \ln|u|.Now we substitute back for u to get the integral in terms of z.\newline12lnu-\frac{1}{2} \ln|u| becomes 12lnz2+1-\frac{1}{2} \ln|z^2 + 1|.Putting it all together, we have:\newlinee2(lnz12lnz2+1)+Ce^2 \cdot (\ln|z| - \frac{1}{2} \ln|z^2 + 1|) + C
  10. Final simplification: We substitute and get:\newlinezz2+1dz=121udu\int -\frac{z}{z^{2}+1} dz = -\frac{1}{2} \int \frac{1}{u} du\newlineWhich integrates to 12lnu-\frac{1}{2} \ln|u|.Now we substitute back for u to get the integral in terms of z.\newline12lnu-\frac{1}{2} \ln|u| becomes 12lnz2+1-\frac{1}{2} \ln|z^{2} + 1|.Putting it all together, we have:\newlinee2(lnz12lnz2+1)+Ce^{2} \cdot (\ln|z| - \frac{1}{2} \ln|z^{2} + 1|) + CFinally, we can simplify a bit by combining the logarithms:\newlinee2lnz(z2+1)12+Ce^{2} \cdot \ln|\frac{z}{(z^{2} + 1)^{\frac{1}{2}}}| + C