Obsolete trig functions and why we don't use them anymore (2013)
I'm not <i>that</i> old, but I learned the haversine formula in a marine navigation class I took through (boy) scouts. Our instructor was a retired merchant navy officer who was somewhat upset that the curriculum didn't include it, and deemed that we should know it.<p>My A-level (≈ AP) maths teacher was mildly amused that I knew it and digressed about log tables. We were (I believe) the last cohort to be issued log-tables, but given the choice in examinations between log-tables, slide-rule, or calculator, we all made the same choice.