P and Q are two points on a uniform ring of resistance R. The equivalent resistance between P and Q is

Explanation

Resistance of section PSQ
`R_(1)=(R )/(2pir).r theta=(R theta)/(2pi)`
Resistance of section PTQ

`R_(2)=(Rr(2pi-theta))/(2pir)rArr (R(2pi-theta))/(2pi)`
As `R_(1) and R_(2)` are in parallel
`"So, "R_("eq")=(R_(1)R_(2))/(R_(1)+R_(2))=(Rtheta(2pi-theta))/(4pi^(2))`