Asymptotic perimeter estimates for spirallike functions

Zain Shayim Alsharari, Toshiyuki Sugawa

By a result of F. R. Keogh in 1959, we have the inequality $L(r,f)/M(r,f)\le 2\pi +4\log [(1+r)/(1-r)]$ for a starlike function $f$ on the unit disk, where $L(r,f)$ and $M(r,f)$ denote…