同学们在学习直线、射线、线段时,因为混淆概念、判别失误等原因容易出现各种各样的错误,下面就同学们在解题中经常出现的错误分析如下。易错点一:弄不清概念而出错例1已知下列语句:(1)线段AB就是A、B两点间的距离;(2)线段AB的中点与线段BA的中点不同;(3)在所有连接两点的线中直线最短;(4)如果AB=BC=CD,则AD=3AB.其中,错误语句的个数是(). Students in the study of straight lines, rays, line segments, because of confusion concept, misidentification and other reasons prone to a variety of errors, the following students often problem-solving errors are analyzed as follows. Easy to make mistakes one: Can not understand the concept of mistakes Example 1 Known the following statement: (1) line segment AB is the distance between A and B points; (2) the midpoint of line segment AB is different from the midpoint of line segment BA; ( 3) The line is the shortest in all the lines connecting two points, and (4) AD = 3AB if AB = BC = CD, where the number of error statements is ().