19.3. (a) Using the chain rule, find ðf/ðz* and df/dz in terms of partial derivatives with respect to x and y. (b) Evaluate d f/əz* and df/ðz assuming that the C-R conditions hold.

Elements Of Modern Algebra
8th Edition
ISBN:9781285463230
Author:Gilbert, Linda, Jimmie
Publisher:Gilbert, Linda, Jimmie
Chapter5: Rings, Integral Domains, And Fields
Section5.4: Ordered Integral Domains
Problem 8E: If x and y are elements of an ordered integral domain D, prove the following inequalities. a....
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hi

My question is about Complex Derivative.

I showed in the upload photo.

z is a complex number and z* is complex conjugate of z.

f(z)=u(x,y)+i.v(x,y);

In section a, we want to obtain the derivative of the function f with respect to z and z * in the Cartesian coordinate system.

In section b, I want to obtain the derivative of the function f with respect to z and z * in the polar coordinate system.
.
In one of the photos, I put a pattern to solve the question.

Thank you very much.

19.3. (a) Using the chain rule, find ðf/ðz* and df/dz in terms of partial
derivatives with respect to x and y.
(b) Evaluate d f/əz* and df/ðz assuming that the C-R conditions hold.
Transcribed Image Text:19.3. (a) Using the chain rule, find ðf/ðz* and df/dz in terms of partial derivatives with respect to x and y. (b) Evaluate d f/əz* and df/ðz assuming that the C-R conditions hold.
For f(z) = u(x, y) + iv(x, y), Definition 19.1.1 yields
df
dz
= lim
Ar-0
u(xo + Ax, yo + Ay) – u(x0, Yo)
Δ+ iΔy
Ay-0
v(xo+Ax, yo + Ay) – v(x0, Yo) ]
Ar + iAy
+i
If this limit is to exist for all paths, it must exist for the two particular paths
on which Ay = 0 (parallel to the a-axis) and Ar = 0 (parallel to the y-axis).
For the first path we get
df
dz
= lim
Ar-0
u(xo+ Ax, yo) – u(xo, yo)
υ (τ0+ Δε, Jo) - υ(ro, Jo)
+i lim
Ar-0
dv
+i
|(x0,y0)
Ax
|(x0.yo)
For the second path (Ax = 0), we obtain
df |
u(xo, Yo + Ay) – u(xo, Yo)
dz
20
= lim
Ay-0
iAy
| n.
|(xo+Y0)
v(xo, Yo + Ay) – v(x0, Yo)
+i lim
Ay-0
iAy
|(x0,Yo)
If f is to be differentiable at zo, the derivatives along the two paths must be
equal. Equating the real and imaginary parts of both sides of this equation
and ignoring the subscript zo (2o, yo, or zo is arbitrary), we obtain
du
dv
du
dv
and
(19.2)
dy
dy
These two conditions, which are necessary for the differentiability of f, are
called the Cauchy–Riemann (C-R) conditions.
The arguments leading to Equation (19.2) imply that the derivative, if it
exists, can be expressed as
in
af
+ i-
(19.3)
dz
fie
||
Transcribed Image Text:For f(z) = u(x, y) + iv(x, y), Definition 19.1.1 yields df dz = lim Ar-0 u(xo + Ax, yo + Ay) – u(x0, Yo) Δ+ iΔy Ay-0 v(xo+Ax, yo + Ay) – v(x0, Yo) ] Ar + iAy +i If this limit is to exist for all paths, it must exist for the two particular paths on which Ay = 0 (parallel to the a-axis) and Ar = 0 (parallel to the y-axis). For the first path we get df dz = lim Ar-0 u(xo+ Ax, yo) – u(xo, yo) υ (τ0+ Δε, Jo) - υ(ro, Jo) +i lim Ar-0 dv +i |(x0,y0) Ax |(x0.yo) For the second path (Ax = 0), we obtain df | u(xo, Yo + Ay) – u(xo, Yo) dz 20 = lim Ay-0 iAy | n. |(xo+Y0) v(xo, Yo + Ay) – v(x0, Yo) +i lim Ay-0 iAy |(x0,Yo) If f is to be differentiable at zo, the derivatives along the two paths must be equal. Equating the real and imaginary parts of both sides of this equation and ignoring the subscript zo (2o, yo, or zo is arbitrary), we obtain du dv du dv and (19.2) dy dy These two conditions, which are necessary for the differentiability of f, are called the Cauchy–Riemann (C-R) conditions. The arguments leading to Equation (19.2) imply that the derivative, if it exists, can be expressed as in af + i- (19.3) dz fie ||
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