Radius of Starlikeness of Convex Combinations of Univalent Starlike Functions
Radius of Starlikeness of Convex Combinations of Univalent Starlike Functions
The radius of starlikeness of the convex combination \[ tf(z) + (1 - t)g(z),\quad 0 < t < 1,\] where $f(z)$ and $g(z)$ are normalized univalent starlike functions, is ${r_u} = 0.4035 \ldots$, the positive root of the equation ${r^6} + 5{r^4} + 79{r^2} - 13 = 0$.