Is the Maximum Modulus Theorem Applicable if E2 is Open and Non-Constant?

  • Thread starter Thread starter laurabon
  • Start date Start date
  • Tags Tags
    Complex analysis
laurabon
Messages
17
Reaction score
0
Homework Statement
Why the sets E1={z∈E:|f(z)|<M} and E2={z∈E:|f(z)|=M}} are both open?
Relevant Equations
E1={z∈E:|f(z)|<M}
E2={z∈E:|f(z)|=M}}
In the maximum modulus therem we have two sets $E1={z∈E:|f(z)|<M}E2={z∈E:|f(z)|=M}}$ I know that the set E1 is open because pre image of an open set. But should't be also E2 closed because pre image of only a point ?
 
Last edited:
Physics news on Phys.org
What is ##f(z)## and what is ##E##? The first, my guess would be, is an analytic function. Also is this the definitions of ##E_1## and ##E_2##? If ##E## is an open set and ##E_2## is defined by ##\{z\in E\;:\;|f(z)|\le M\}##, then ##E_2## and ##f## is not constant, then ##E_2## is also open because the maximum is achieved on the boundary not in ##E##. But these are just guesses. You should give all the information.
 
  • Like
Likes FactChecker
Prove $$\int\limits_0^{\sqrt2/4}\frac{1}{\sqrt{x-x^2}}\arcsin\sqrt{\frac{(x-1)\left(x-1+x\sqrt{9-16x}\right)}{1-2x}} \, \mathrm dx = \frac{\pi^2}{8}.$$ Let $$I = \int\limits_0^{\sqrt 2 / 4}\frac{1}{\sqrt{x-x^2}}\arcsin\sqrt{\frac{(x-1)\left(x-1+x\sqrt{9-16x}\right)}{1-2x}} \, \mathrm dx. \tag{1}$$ The representation integral of ##\arcsin## is $$\arcsin u = \int\limits_{0}^{1} \frac{\mathrm dt}{\sqrt{1-t^2}}, \qquad 0 \leqslant u \leqslant 1.$$ Plugging identity above into ##(1)## with ##u...
Back
Top