(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

See the picture for the situation of the problem.

I'm told that any ray starting from S and getting through the "Cartesian Oval" reach point P.

I must show that the equation of the interface curve is [tex]l_0n_1+l_i n_2=K[/tex] where K is a constant.

So far I've showed that [tex]l_0=\sqrt {x^2+y^2}[/tex] and [tex]l_i=\sqrt {y^2+(s_0 + s_i -x)^2}[/tex]. But I remain stuck as how to proceed further.

Any idea is greatly appreciated.

2. Relevant equations

Snell's law? I've tried something with it but didn't reach anything.

Maybe Fermat's principle?

3. The attempt at a solution

See above.

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# Homework Help: Cartesian Oval

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