MHB Laplace equation and Median Value Property

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The discussion revolves around solving the Laplace equation \(u_{xx} + u_{yy} = 0\) within the unit disk, where the boundary condition is given as \(u(x,y) = x\) on the circle defined by \(x^2 + y^2 = 1\). Participants are asked to find the value of \(u\) at the origin \((0,0)\) using the median value property of harmonic functions. The median value property states that the value of a harmonic function at a point is the average of its values over any circle centered at that point. The solution involves evaluating the average of the boundary condition over the unit circle, leading to the conclusion that \(u(0,0) = 0\). The discussion highlights the application of harmonic functions and their properties in solving boundary value problems.
Julio1
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Suppose that $u$ is the solution of the Laplace equation

$u_{xx}+u_{yy}=0$ in $\{(x,y)\in \mathbb{R}^2: x^2+y^2<1\}$

$u(x,y)=x$ for all $(x,y)\in \mathbb{R}^2$ such that $x^2+y^2=1.$

Find the value of $u$ in $(0,0).$ Use the property of median value.
Hello. The median value is $u(x)=\dfrac{\displaystyle\int_{\partial B(x,r)} u(y)dS(y)}{\displaystyle\int_{\partial B(x,r)} \, dS(y)}$. But how can apply for this case?
 
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Hello :). I don't can solve this... Can any help me?
 

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