I ran into one of my old slide rules today! Not my good one (a Pickett that I don't know where it is now). I found my backup cheap plastic Sterling Precision (figures!) But it's got the basic C, D, CI, A, B, K, L, S and T scales.
So I had to see what I remembered about how to use a slide rule. That turned out to be "not much", but I found an instruction sheet online and I've been practicing today.
Multiplication and division - I could still remember that
Squaring and cubing - that knowledge was still resident in my brain too
Square roots and cube roots - I had to review a bit (I had forgotten the rule that tells you which part of repeating scales to use)
I am still confused by the rule for cube roots. I need more practice! (Or maybe I should just not try to do cube roots!)
Logarithm (base 10) - I remembered that mostly (I had to think for a second about adding "1" for each power of ten - brain fart)
e.g., log(5) = 0.699, therefore log(50) = 1+0.699, log(500) = 2+0.699, log(5000) = 3+0.699
Sine - direct read (had to think for just a minute to remember "complementary angles" rule to get cosine)
e.g., cos(X) = sin(90-X)
Tangent - had to look this one up (I had forgotten how to get tangent of > 45 degrees when you go off scale)
e.g., tan(X) = 1 / tan(90-X)
Since my tangent scale goes from 5.8 to 45 degrees, I still don't know how you get the tangent of an angle less than 5.8 degrees or greater than 84.2 degrees
My mind has gotten very weak it appears. "Use it or lose it", ... and I haven't used it! Good thing I only found my backup slide rule that has very few scales on it. No way could I even come close to remembering how to use all the scales on my Pickett (wherever it is).
I have to go and relearn how and why you use the "C inverted" scale. I think it's so you don't have to move the slide so much, but my brain farted again when I tried to remember how to do that.
If was fun doing all this today. Embarrassing with the mathematics and slide rule techniques I had forgotten ... but fun. I figure if I set aside a slide rule for dead-calculator-battery post-SHTF cipherin' (as Jethro would say), maybe I ought to set aside an instruction manual too! On the bright side, I can't come up with many post-SHTF needs for finding a cube root of something. Or the logarithm either. But using the tangent - now that might be useful for post-SHTF construction projects.
Have been sleeping with the windows open which is wonderful.
