题目

What are you going to do if you are in a burning house? How will you escape? Do you know how to save yourself? Please read the following passage. Escaping a fire is a serious matter. Knowing what to do during a fire can save your life. It is important to know the ways you can use and show them to everyone in the family, such as stairways and fire escapes, but not lifts. From the lower floors of the buildings, escaping through windows is possible, learn the best way of leaving by windows with the least chance of serious injury. The second floor window is usually not very high from the 如图，在正方形ABCD中，对角线AC与BD相交于点E，AF平分∠BAC，交BD于点F，求证：EF+12AC=AB．