Find the equivalent resistance for the infinite

network shown in Figure P2.12(a). Because of

its form, this network is called a semi-infinite

ladder. [Hint: If another section is added

to the ladder as shown in Figure P2.12(b),

the equivalent resistance is the same. Thus,

working from Figure P2.12(b), we can write

an expression for Req in terms of Req. Then,

we can solve for Req.]