题目

Honesty is the best policy，as the English saying goes.Unfortunately，honesty often leaves us when no one is watching，British psychologists reported last week. Researchers at UK's Newcastle University set up an experiment in their psychology department's coffee room. They set a kettle，with tea，coffee and milk on the counter and hung up a sign listing the price for drinks.People helping themselves to a cup of tea were supposed to put a few cents in the box nearby. The scientists hung a poster above the money box，and changed each week between pictures of gazing(注视的)eyes如图，BF⊥AC，CE⊥AB，BE=CF．求证：AD平分∠BAC．