Turkish NMO First Round - 2012 Problem - 09 {Geometry}
Source:
July 1, 2012
geometry
Problem Statement
The chord [CD] of the circle with diameter [AB] is perpendicular to [AB]. Let M and N be the midpoints of [BC] and [AD], respectively. If ∣BC∣=6 and ∣AD∣=23, then ∣MN∣=?<spanclass=′latex−bold′>(A)</span>4<spanclass=′latex−bold′>(B)</span>32<spanclass=′latex−bold′>(C)</span>21<spanclass=′latex−bold′>(D)</span>5<spanclass=′latex−bold′>(E)</span>None