Question 28In triangle $ABC,$ sides $a,$ $b$ and $c$ are opposite angles $A,$ $B$ and $C$ respectively. $\overline{AD}$ bisects angle $A$ and meets $\overline{BC}$ at $D.$ Then if $x=CD$ and $y=BD$ the correct proportion is:$\dfrac xa=\dfrac a{b+c}$$\dfrac xb=\dfrac a{a+c}$$\dfrac yc=\dfrac c{b+c}$$\dfrac yc=\dfrac a{b+c}$$\dfrac xy=\dfrac cb$