we know that
1) PD=PB= radius of the circle P
2) initially PDB is an isosceles triangle. because has two sides equals
so
m ∠ DBP=m ∠ PDB
m ∠ DBP+m ∠ PDB+m ∠ DPB=180
m ∠ DBP=[180-60]/2------> m ∠ DBP=60
3) if m ∠ DBP=60°
then
the 3 angles are equals
PDB is an equilateral triangle
therefore
the answer is
m ∠ DBP=60°
