[Bob the Science Guy] remembers how to use a slide rule. Even after all these years, it is pretty easy to remember how to multiply and divide. If you can’t remember, you can usually work it out, as long as you understand how slide rules work. But what about sine, cosine, and quadratics? [Bob’s] been making videos about topics like this, and if you’ve wanted to put your slide rule collection to practical use, you’ll enjoy these videos. You can see one below.

The trick to the slide rule is that it is deceptively simple. You are in effect adding logarithms and then taking an antilog. The issue is that you still have to have some intuition about the scale of the answer since 2×3 works out the same as 2×3000 or 200×300.

But it is even trickier than that. Adding and subtracting is not easy on the slide rule. [Bob] shows how to use your math skills to convert problems that might have been addition problems into trig problems. So while it might seem more complicated to use trig, it may help work the problem on the slide rule.

We like slide rules. If you don’t have one, try this one in your browser (hint: go full screen and show both sides).