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One or two arrows on a coordinate axis?
Posted:
Jan 19, 2012 8:28 PM
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I've always thought that a cartesian coordinate axis consists of
(1) a straight line with a distinguished point representing 0,
(2) an orientation, indicated by an arrow, that indicates the
direction of increasing coordinate values, and
(3) a unit, representing 1, located away from 0 on the side
of the arrow:
0 1
-----------------------------------|---------|------------------------------
------>
Recently, in discussions with fellow instructors at a Ph.D.
granting university, I became aware that there are actually
two "camps" regarding this issue:
(I) One arrow on each axis, as described above, and
(II) Two arrows on each axis (presumably to indicate that
the axis is supposed to be extended indefinitely at both ends),
0 1
<-----------------------------------|---------|-----------------------------
------->
as exemplified by this statement:
>>>
It's not anything that I've ever thought about before, but I'd probably
consider myself in the "double-arrow camp" on the axes.
>>>
Any comment or clarification on this matter will be much appreciated.
John Lee
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