Find p(t) for the ODE given that the

Perla Benitez

Perla Benitez

Answered question

2022-04-14

Find p(t) for the ODE given that the Wro
ian is a non-zero constant.
Consider an ODE of the form d2x dt 2+p(t) dx  dt +q(t)x=0
Suppose that we have two solutions x1(t) and x2(t) to this ODE and their Wro
ian is a non-zero constant. That is,
W[x1,x2]=C0
What is p(t)? (Find an explicit formula).
The formula for the Wro
ian is
W[x1,x2]=x1 dx 2 dt x2 dx 1 dt 
Since the Wro
ian is non-zero, we know that x1 and x2 are independent. This means that  dx 1 dt  and  dx 2 dt  are such that all variables cancel out. I'm not sure how to proceed from here. Can I get some hints on how to find p(t)? Thanks
Edit: Using Abel's theorem, we know that if x1 and x2 are solutions to the ODE then
W[x1,x2]=Aep(t) dt 
Then this can be used to solve for p(t).
W[x1,x2] =Aep(t)dt=C ep(t)dt=CA  p(t)dt=ln(CA) p(t)=ddt(ln(CA))  =0
So p(t)=0.

Answer & Explanation

pobijedi6wro

pobijedi6wro

Beginner2022-04-15Added 15 answers

Explanation:
If xi +pxi+qxi=0,u=1,2, then
x1(x2''+px2'+qx2)=x2(x1''+px1'+qx1)=0

 (x1x2''x1''x2)+p(x1x2'x2x1')=0

 p=x1x2''x1''x2x1x2'x2x1'

=x1x2''x1''x2W[x1,x2]

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