Explanation:
Number 1
1. Construct AB (Construction)
2. MA = AN = NB = BM (Construction - same radius means same length)
3. MANB is a rhombus (Def. of rhombus)
4. MN is perpendicular bisector of AB (Diagonals bisect each other, Diagonals are perpendicular - properties of rhombus)
Number 2
1-3 are same as first proof
4. AB is perpendicular bisector of MN (Diagonals bisect each other, Diagonals are perpendicular - properties of rhombus)
Hope this helps!