Imagine making a vertical cut to the right of the first R3.
Right.
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It is worth thinking about the _idea_ behind this method of solution,
because the idea comes up again and again. Indeed this idea is
closely related to the very definition of infinity.
Here's a non-electrical purely-mathematical example. R is
defined by in infinitely recursive formula
R = crt(6 + crt(6 + crt(6 + crt(6 + ...)))) [A]
where crt stands for cube root.
Equation [A] or one of its congeners tends to show up on the high
school math contest every year. The algebra is dead simple; the
only challenge is to understand what "..." means.
Another word for this type of problem is "iterated map". The value R
is a "fixed point". Iterated maps show up a lot in physics, including
dynamics, including chaotic dynamics.