MN is the perpendicular bisector of AB. Which of the given statements is correct?

(i) ∠ANM + ∠MNB = 90∘
(ii) AN = NB
(iii) AN = 2NB
(iv) ∠MNB = $\frac{1}{2}$∠ANM

NM ⊥ AB and NM divides AB into two congruent parts.

Clearly ∠ANM = ∠MNB = 90^∘ is true. AN = NB is true since NM ⊥ AB , AN = 2NB  is false, and ∠MNB = $\frac{1}{2}$∠ANM is false. 

Thus, only (i) and (ii) are correct.