Comment on 'On the locus formed by the maximum heights of projectile motion with air resistance'

We show that a remark made by Hernández-Saldaña in 2010 (Eur. J. Phys. 31 1319) concerning the validity of an expression first presented by us in 2006 (Proc. 17th Biennial Congress of the Australian Institute of Physics Paper 27) for the optimal angle of projection for greatest forward skew in the trajectory of a projectile launched in a linear resisting medium is in error. We also draw attention to an earlier treatment (2006 Int. J. Math. Educ. Sci. Technol. 37 411) of the locus of apexes for such a projectile. When expressed in Cartesian form, the locus can be written in terms of the nowfamiliar, though less common, secondary real branch of the Lambert W function. © 2011 IOP Publishing Ltd.