I tried for more than an hour to solve the below problem but got nothing. I tried to make a copy and flip it vertically and attach it to the original shape but no more happened.
$AB=9,DC=16\\AO=OD$ 
This is half of a circle . I don't how apply $distance -of -A- to -circle=distance -of -B- to -circle$ as a result of $AO=OD$
Can someone help me to start to sloving,please?
Implicitly I tied two below figure
