Problem 3 Points A,B,C,DA,B,C,DA,B,C,D are on a circle with radius RRR . ∣AC∣=∣AB∣=500|AC|=|AB|=500∣AC∣=∣AB∣=500 , while the ratio between ∣DC∣,∣DA∣,∣DB∣|DC|, |DA|, |DB|∣DC∣,∣DA∣,∣DB∣ is 1,5,71,5,71,5,7 . Find RRR .