**by Neal R. Wagner**

**Copyright © 2001 by Neal R. Wagner.
All rights reserved.**

**
NOTE: This site is obsolete. See book draft (in PDF):**

This is a lesson from prehistoric times. It brings back nostalgic
memories. Before calculators, one used *printed tables* to
carry out calculations. The example in the main section was
to calculate ** 23.427 * 23.427 * 3.1416**.
To do this, one first needed the logarithms (base 10) of the two numbers.
In

Number Logarithm2342 36959using interpolation entry: 23427 3697167th entry under18is12.62343 36977take 369590 + 126 to get 369716

This means that ** log(2.3427) = 0.369716** approximately.
Then

Similarly, look up ** 3.1416**:

Number Logarithm3141 49707using interpolation entry: 31416 4971546th entry under14is8.43142 49721take 497070 + 84 to get 497154

This means that ** log(3.1416) = 0.497154** approximately.

Form the sum: ** 1.369716 + 1.369716 + 0.497154 =
3.236586** (this must be done by hand, with pencil and paper).

Now finally, one has to look up the ``anti-log'' in the same table:

Number Logarithm1724 23654using interpolation entry: 17242 236592nd entry under25is5.01724 23679take 17240 + 2 to get 17242

This means that ** log(1.7242) = 0.23659** approximately,
so

All this pain just to multiply 3 numbers together,
to get 4 or 5 digits of accuracy in the answer.
The next two lessons from our primitive ancestors:
how to use tables of the *logarithms* of trig functions (to save
one lookup), and how to use a slide rule. (Just kidding.)