说明：  边角边全等三角形演示课件，帮实习学校老师做的，懂action的交流，懂隐形按钮的下，都不懂的别下了，免得说是垃圾！
(Corner Pin congruent triangles demonstration courseware, training schools to help teachers do, and understand the action exchanges, understand the stealth button, nothing under the other, so that was rubbish!)