## Geometry: Common Core (15th Edition)

The Segment Addition Postulate tells us that $AE+EY=AY$ Since $AE=EY$, we can substitute AE for EY in the formula. $AE+AE=AY$ Combine like terms. $2AE=AY$ divide each side by 2 $2AE\div2=AY\div2$ $AE=\frac{1}{2}AY$