numbers as “complex numbers with imaginary part zero.” Thus Ö2 was
regarded as real and Ö2+i0 as complex. These were conveniently considered as
being distinct entities or the same, depending on the circumstances, without
causing any cognitive conflict. They only become cognitive conflict factors
when evoked simultaneously.
In certain circumstances cognitive conflict factors may be evoked
subconsciously with the conflict only manifesting itself by a vague sense of
unease. We suggest that this is the underlying cause for such feelings in
problem solving or research when the individual senses something wrong
somewhere; it may be a considerable time later (if at all) that the reason for the
conflict is consciously understood.
A more serious type of potential conflict factor is one in the concept image
which is at variance not with another part of the concept image but with the
formal concept definition itself. Such factors can seriously impede the learning
of a formal theory, for they cannot become actual cognitive conflict factors
unless the formal concept definition develops a concept image which can then
yield a cognitive conflict. Students having such a potential conflict factor in
their concept image may be secure in their own interpretations of the notions
concerned and simply regard the formal theory as inoperative and superfluous.
The notions so far described are all clearly manifested in the various
concepts of limit and continuity. In the remainder of the article we describe a
few of the problems caused by a concept image which does not coherently
relate to the concept definition and the resulting potential conflicts.
2. Practical curriculum problems
There are several practical problems imposed in the teaching of the concepts of
limits and continuity. If we confine ourselves to the three notions set out:
(i) limit of a sequence lim
n®¥
sn,
(ii) limit of a function lim
x®a
f (x),
(iii) continuity of a function f: D®R,
then we find that in English schools these are rarely taught in a logical order.
Practical considerations and the need to learn the calculus at the earliest
opportunity lead to the notion of a limit of a function first being discussed in
differentiation as
lim
dx®0
f (x +dx) - f (x)
dx