Which Solution Should You Choose for a Given Bernoulli Problem?

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supercali
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The problem that was given:
[tex]{\frac {d}{dx}}y \left( x \right) =2\,{\frac {x}{{x}^{2}\cos \left( y<br /> \right) +4\,\sin \left( 2\,y \right) }}[/tex] after doing some changes we get a bernuli that looks like this
[tex]2\, \left( {\frac {d}{dy}}x \left( y \right) \right) x \left( y<br /> \right) =\cos \left( y \right) \left( x \left( y \right) \right) ^{<br /> 2}+4\,\sin \left( 2\,y \right)[/tex]
with the initial conditions that x=f(y) goes through (1,0) (1=x,0=y)
the solution is
[tex]\left( x \left( y \right) \right) ^{2}=-8-8\,\sin \left( y \right) +<br /> 9\,{{\rm e}^{\sin \left( y \right) }}[/tex]
for these conditions the boundary is Dy=(arcsin(ln(8/9)),pi/2) which includes the point in the initial conditions the only problem i have is i don't know how to choose the final solution for x(y) thus whether is it th possitive root or the negative one
 
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supercali said:
with the initial conditions that x=f(y) goes through (1,0) (1=x,0=y)

the only problem i have is i don't know how to choose the final solution for x(y) thus whether is it th possitive root or the negative one

Hi supercali! :smile:

But if it goes through (1,0), with x = 1, then it must be the positive solution, mustn't it? :confused:
 
how stupid of me how did i not notie that?
after solving this creepy thing i must have been too exhausted :-)