Solution of nonlinear BVP is symmetric where derivative is 0: For the following nonlinear BVP, N

g2esebyy7

g2esebyy7

Answered question

2022-04-23

Solution of nonlinear BVP is symmetric where derivative is 0:
For the following nonlinear BVP,
y(x)+y(x)2=0, y(0)=y(1)=0,
I wish to show that if
y(x0)=0, then y(x)=y(x0x).
That is, the solution is symmetric about this point.
I've already shown that the nontrivial solution is unique, so it should be enough to show that z(x)=y(x0x) satisfies the BVP where y is a nontrivial solution but I can't seem to do this.

Answer & Explanation

Jonas Dickerson

Jonas Dickerson

Beginner2022-04-24Added 22 answers

Step 1
You make a little error, the reflection of x at x0 has the formula
τ(x)=2x0x.
Then at the reflection point you have τ(x0)=x0, so it is indeed a fixed point of the reflection.
You have now a point x0, y0=y(x0) and y(x0)=0
Next you consider with the corrected reflection z(x)=y(2x0x) and get likewise z(x0)=y(x0)=y0 and z(x0)=y(x0)=0.
Additionally z is a solution of the DE. By uniqueness z=y follows.
To progress further you probably have to use next that any solution is concave, so has at most two roots.

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