一、以旧联新,搭桥铺路采用“温故而知新”的办法,在投影片的设计上要找准新旧知识的联结点,并因情况而异采用不同的方式。一种是联想式。如在教“环形面积的计算”时,可做2幅抽拉投影片。在教学时,先出示2个半径分别为5 cm和2 cm的圆,让学生先计算出 First, the old couplets new, bypass bridge paving the way to “learn from the old” way, in the design of the projection film to find out the juncture of old and new knowledge, and use different ways depending on the circumstances. One is associative. If you teach “calculation of the ring area ”, you can do two drawing slide. In teaching, first show two circles with radius of 5 cm and 2 cm respectively, so that students can calculate