In a recent paper1 L. Edward Millet proposed a justification of an approximation for the period of a simple pendulum suggested earlier by Kidd and Fogg,2 and made the argument that the expression should be included in textbooks. This paper presents two other approximations that are more accurate. At this point it would seem that a decision as to which approximation, if any, should be included in textbooks or lab manuals is premature.

1.
L. Edward
Millet
, “
The large-angle pendulum period
,”
Phys. Teach.
41
,
162
163
(March
2003
).
2.
R. B.
Kidd
and
S. L.
Fogg
, “
A simple formula for the large-angle pendulum period
,”
Phys. Teach.
40
,
81
83
(Feb.
2002
).
3.
K.R. Symon, Mechanics, 3rd ed. (Addison-Wesley, Reading, MA, 1960), pp. 209–212.
4.
R.S. Burington, Handbook of Mathematical Tables and Formulas (Handbook Publishers, Sandusky, OH, 1947), pp. 93, 263.
5.
M. I.
Molina
, “
Simple linearization of the simple pendulum for any amplitude
,”
Phys. Teach.
35
,
489
490
(Nov.
1997
). Molina had obtained this expression previously using power series argument.
6.
W. P.
Ganley
, “
Simple pendulum approximation
,”
Am. J. Phys.
53
(
1
),
73
76
(Jan.
1985
).
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