课本中的许多习题,看似平常,却有着丰富的内涵。教学中要立足课本,着眼提高,就应善于利用课本中的每道习题,将它从特殊推广到一般,发挥其“模型”功能,重视其广泛应用。现举一例,谈一点粗线体会:《几何》第二册P24第9题:“已知,如图1,AC⊥AB,BD⊥AB,AD与BC相交于E,EF⊥AB,垂足为F,又AC=p,BD=q,EF=r,求证:(1/p)+(1/q)=(1/r)”。 Many exercises in textbooks seem ordinary, but they have rich connotations. In teaching, we must base ourselves on textbooks and focus on improvement. We should be good at using every problem in textbooks, promote it from special to general, and use its “model” function to emphasize its wide application. Let’s take a case and talk about the thick line experience: Geometry II Book P24 Problem 9: “Known, Figure 1, AC⊥AB, BD⊥AB, AD and BC intersect at E, EF⊥AB, Pedal F, AC=p, BD=q, EF=r, verification: (1/p)+(1/q)=(1/r)”.