ABSTRACT
The Standards (NCTM, 1989) suggest a change in the role of proof in our mathe-
matics curriculum. The call is for a decrease in attention given to Euclidean geometry as an axiomatic system and two-column proofs. At the same time, it is recommended that short sequences of theorems be developed and that deductive arguments be expressed orally and in paragraph or sentence form. Suppose the desire is to prove the base angles of an isosceles triangle are congruent using the typical two-column proof as well as paragraph form. In Fig. 8.2 you are given triangle DEF with DE= DF. Prove ZDEF = Z.DFE.
