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问题: 一道几何题

已知角A=角B,AA1、PP1、BB1均垂直于A1B1,AA1=17,PP1=16,BB1=20,A1B1=12,则AP+PB等于

解答:

解: 延长BP交AA1于C,做CD⊥BB1于D.
∵AA1⊥A1BA BB1⊥A1B1
∴AA1∥BB1 ∴∠B=∠PCA=∠A ∴PA=PC
∵BB1⊥A1B1
∴CD=BB1
过P做EF∥BB1 交AA1于E,BB1于F
∵AA1⊥A1BA BB1⊥A1B1 PP1⊥A1BA
∴则EA1=PP1=16 AE=AA1-PP1=17-16=1
BF=BB1-PP1=20-16=4
∵PA=PC EF⊥AA1 ∴AE=CE=1
FD=CE=1
∴BD=5
BC=BP+AP=√[(CD)^+(BD)^]=5√17