calculators did not exist as we´ve got them today. they had small tables you could move sideways against each other, works pretty good and if you got enough practice it is fast enough.
i build a small html to show you what i meant with the dynamic geometry. scroll down to select the range etc.
its not very exact in html-modus. the version edited in the programm is already pretty good.
http://mitglied.lycos.de/myphpspace/...d/course1.html
sorry, it needs a java applet, i hope it works on your pcs.
here is a screen too:
