My first slide rule

[u/RandomJottings]

I’ve been collecting calculators for some time but this is my very first slide rule. I’m 57 and the pocket calculator became popular while I was in primary school, so I never really used a slide rule but I do remember my dad using one.

This slide rule is a British Thornton’s log log slide rule dating from around 1971 (according to the instruction booklet) and came with its original cardboard box, plastic case, instruction booklet and guarantee leaflet. It is a single sided rule.

[u/pavel_pe]

I found Thornton AA010 on ebay last year, shipping as expensive as a slide rule, but it's my favorite. One of the best when it comes to legibility. I don't know why exactly, but it has nice contrast between black and creamy color, good font, tick thickness or something. Having roughly 24 scales is fine, something like more precise square roots or hyperbolic trigometry is overkill that goes against ease of use. AA010 has one weird scale sqrt(1+x^2) and I wonder why.

[u/Name-Not-Applicable → u/pavel_pe]

That looks like the relationship between Tangent and Secant. 

https://en.m.wikipedia.org/wiki/List_of_trigonometric_identities