or each of the given functions find the set of points on which the Cauchy-Riemann equations aresatisfied. Also, check whether the function is analytic or not on the points where Cauchy-Riemannequations are satisfied.(a) 𝑓 (𝑧) = |𝑧|2
Question
or each of the given functions find the set of points on which the Cauchy-Riemann equations aresatisfied. Also, check whether the function is analytic or not on the points where Cauchy-Riemannequations are satisfied.(a) 𝑓 (𝑧) = |𝑧|2
Solution
The function given is f(z) = |z|^2.
First, let's express this function in terms of x and y, where z = x + iy. So, f(z) = |x + iy|^2 = x^2 + y^2.
The Cauchy-Riemann equations are two partial differential equations which are satisfied by a function if it is analytic. They are given by:
- ∂u/∂x = ∂v/∂y
- ∂u/∂y = -∂v/∂x
Here, u = x^2 + y^2 and v = 0 (since the function f(z) is purely real).
Let's calculate the partial derivatives:
∂u/∂x = 2x ∂u/∂y = 2y ∂v/∂x = 0 ∂v/∂y = 0
Now, let's check if the Cauchy-Riemann equations are satisfied:
- ∂u/∂x = ∂v/∂y => 2x = 0
- ∂u/∂y = -∂v/∂x => 2y = 0
From the above equations, it is clear that the Cauchy-Riemann equations are satisfied only at the point (0,0).
However, for a function to be analytic, it must satisfy the Cauchy-Riemann equations not just at a point, but in a neighborhood of that point. Since the given function does not satisfy this condition, it is not analytic.
Similar Questions
For each of the given functions find the set of points on which the Cauchy-Riemann equations aresatisfied. Also, check whether the function is analytic or not on the points where Cauchy-Riemannequations are satisfied.(a) 𝑓 (𝑧) = |𝑧|2(b) 𝑓 (𝑥 + 𝑖𝑦) = 𝑥3 + 𝑖(𝑦 − 1)3(c) 𝑓 (𝑥 + 𝑖𝑦) = 𝑥2 + 𝑖𝑦2(d) 𝑓 (𝑧) = Re(𝑧)
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when we say a function is analytic
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