Need help on circle work
Please help me . I don't understand how to do this work.

Answer:
Step-by-step explanation:
Radius = OC = OD + DC = 6 + 4 = 10
In ΔODB, OB = radius = 10, OD = 6, so
[tex]DB=\sqrt{OB^2-OD^2}=\sqrt{10^2-6^2}=8\\[/tex]
Similarly, AD = 8
Then AB = AD + DB = 16