Question

find the equivalent resistance of this infinite ladder of resistors:
http://i.stack.imgur.com/n1eIX.jpg

Answer 1

I've somewhere seen the solution looking like this:

\[R_{eq}=R+R||R_{eq}\]
isn't it just an approximation?

Answer 2

take advantage of the fact that the wire extends upto infinity..
so say the equivalent resistance for the entire circuit on one side of a particular loop(extending upto infinity on that side) is Requivalent. By symmetry it may be argued that the equivalent resistance for the next loop(on the finite bounded side on the chosen loop) is also Requivalent(as the wire extends upto infinity the loops cannot be distinguished) ..so now write the equation.