Given:
Apparent dip shown by the needle of the dip circle, δ1 = 45°
Dip shown by the needle of the dip circle on rotating the circle, δ2 = 53°
True dip is given by
Cot2 δ = Cot2 δ1 + Cot2 δ2
Cot2 δ = Cot2 45° + Cot2 53°
Cot2 δ = 1.56
Cot2 δ = 1.56
δ = 38.6° ≈ 39°