My try : AB = 1, BD = √3 , OA = OB = OD = 1, Let AD be x
The given circle of radius 1 is also circum-circle of Δ ABD
∴ R = 1 for Δ ABD
∴ a/Sin A = 2R
∴ √3/Sin A = 2R = 2
∴ Sin A = √3/2
∴ A = 60°
and hence C = 120°
Also by cosine rule on Δ ABD,
(√3)² = 1² + x² −2x cos60°
or x² −x −2 = 0
∴ x = 2 What to do next

Note that $\triangle{AOB}$ is equilateral, $\triangle{BOD}$ is isosceles and $\cos \angle{OBD}=\frac{\sqrt{3}}{2} \to \angle{OBD}=30° \to \angle{ABD}=90°$. $AD$ is a diameter so $AD=2$. Can you finish?