在北师大版教材八年级数学下册有这样一道习题:如图1,甲、乙两个单位分别位于一条封闭街道的两旁,现准备修建一座过街天桥,天桥建在何处才能使由甲到乙的路线最短?注意:天桥必须与街道垂直.答案:如图2,将点A沿与街道垂直的方向平移,平移距离等于桥长,到达点A_1,连接A_1B,与街道靠近B的一侧交于点B_1,过B_1点建桥即符合要求.探究一:如图3,如果甲、乙分别位于两条平行封 In the Beijing Normal University version of textbooks eighth grade mathematics book has such a problem: Figure 1, A, B two units are located on both sides of a closed street, is now ready to build a cross street bridge, where the flyover can be made from A to Answer: As shown in Figure 2, point A is translated in a direction perpendicular to the street, and the translation distance is equal to the length of the bridge, reaching point A_1, connecting A_1B, and side of the street close to B To point B_1, over B_1 bridge is built to meet the requirements. Inquiry A: As shown in Figure 3, if A, B were located in two parallel seal