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在几何计算中,若题目没有给出图形,一般情况下图形的大小、形状、位置是不确定的,解决问题时需要分类讨论,但许多学生常受思维定势的影响,造成解题不圆满,这都是“无图”惹的祸.一、直线例1已知:线段AB的长为25cm,点C在直线AB上,且AC长为5cm,求线段BC的长.分析因为点C的位置未确定,它可能在点A的左边,也有可能在点A的右边,要分类讨论.解:①若点C在线段BA的延长线上,则BC=25+5=30
In the geometric calculation, if the title does not give a graph, the size, shape and position of the graph are generally indefinite. Solving the problem needs to be classified and discussed. However, many students are often influenced by the thinking tendency, which leads to the incomplete solution. , This is The first line 1 is known: the length of the line segment AB is 25cm, the point C in the straight line AB, and AC length of 5cm, find the length of the line BC analysis The location of point C is undetermined, it may be to the left of point A and possibly to the right of point A. Solution: ① If point C is on the extension of line BA, then BC = 25 + 5 = 30