The figure below shows three squares ABCD, A1B1CD1, and A1B2C2D2. If M is
the midpoint of BB2, prove that (1) B1M is perpendicular to DD2;
(2) DD2 = 2B1M.
Machu Picchu called the "Lost City of the Incas" is one of the New Seven Wonders of the World and UNESCO World Heritage Site.