Math Problem Statement

Evaluate ∫_C z̅ dz along the following contour, the line segment from the origin to 1+i.

Solution

The question asks to evaluate the contour integral Czdz\int_C \overline{z} \, dz along a specific path CC, which is the line segment from the origin 00 to 1+i1 + i.

Solution

  1. Parameterize the Path CC: The line segment from 00 to 1+i1 + i can be parameterized by setting z(t)=t+itz(t) = t + it, where tt goes from 00 to 11.

  2. Express dzdz: Taking the derivative with respect to tt, we get: dzdt=1+idz=(1+i)dt\frac{dz}{dt} = 1 + i \Rightarrow dz = (1 + i) \, dt

  3. Express z\overline{z}: The complex conjugate of zz along this path is z=tit\overline{z} = t - it.

  4. Set Up the Integral: Substitute z=tit\overline{z} = t - it and dz=(1+i)dtdz = (1 + i) \, dt into the integral: Czdz=01(tit)(1+i)dt\int_C \overline{z} \, dz = \int_0^1 (t - it)(1 + i) \, dt

  5. Simplify the Integrand: Expanding (tit)(1+i)(t - it)(1 + i): (tit)(1+i)=t+ititi2t=t+t=2t(t - it)(1 + i) = t + it - it - i^2 t = t + t = 2t So, the integral simplifies to: 012tdt\int_0^1 2t \, dt

  6. Evaluate the Integral: Now we have a simple real integral: 012tdt=201tdt=2[t22]01=212=1\int_0^1 2t \, dt = 2 \int_0^1 t \, dt = 2 \left[ \frac{t^2}{2} \right]_0^1 = 2 \cdot \frac{1}{2} = 1

Answer

The value of the contour integral is: Czdz=1\int_C \overline{z} \, dz = 1

Would you like more details on any part of this solution, or do you have further questions?

Related Questions:

  1. How would the solution change if the path CC were different, such as a circular arc?
  2. Can we use this method for a general complex function, or does it work only for certain types?
  3. What is the role of conjugation in complex integration, and how does it affect the result?
  4. How do contour integrals apply in the context of complex analysis?
  5. What are some applications of complex integration in physics and engineering?

Tip

When solving contour integrals involving conjugates, make sure to parameterize correctly and carefully handle the conjugation within the integrand.

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Math Problem Analysis

Mathematical Concepts

Complex Integration
Contour Integrals
Complex Conjugates

Formulas

z(t) = t + it (parameterization of the line segment from 0 to 1 + i)
dz = (1 + i) dt
∫_C z̅ dz = ∫_0^1 (t - it)(1 + i) dt

Theorems

Complex Line Integrals

Suitable Grade Level

College Level