That's when you pulled out your trusty slide-rule. I never used one but my EE teachers always talked about them.

My dad, a mechanical engineer passed his ruler to me. It was almost a mini ceremony of sorts. It was special to him , but by that time nobody used them, and aside for some playing with it a bit I never used it for anything else.

A similar thing happened to me, as a teenager 25ish years ago - an elderly relative gave me a slide-rule and told me it could be useful to me in my physics career.

Part of me wishes I'd kept it, but even at the time I was given it the thing was obsolete.

There isn't a method of calculating trig functions with less than 30 steps?