The bisector of exterior angle of $B$ intersects the bisector $CF$ ($F$ on $AB$) at $Y$. Determine the comparison of $YF : YC$ by considering $a, b, c$ as the lengths of side of the triangle $ABC$
I am stuck in this problem. I am learning about bisector theorems. What theorems should I use here? Or what theorems should I apply first? I have read some of textbook about this, but found no hint.
We get $$\frac{YF}{YC}=\frac{BF}{a}$$ with $$BF=\frac{ac}{a+b}$$ we get $$\frac{YF}{YC}=\frac{c}{a+b}$$