Let A be the position of a person on the bank of a river and OP the tree on the opposite bank and ∠OAP = 60°. When the person retires to the position B, s.t. AB = 40 m then ∠ OBP = 30° Let OA = x m and OP = h m In Δ OAP, OP = OA tan 60° = x√3 and in Δ OBP, OP = OB tan 30° =