Monday, May 13, 2019
--- Mental math ---
If you plan to study mathematics on the trail (or the street, or in class, or at museums), or you just want to keep track of your purchases at the grocery store you have to add one more piece of equipment to your ensemble, a calculator....or maybe not.
Arithmetic calculations such as addition, subtraction, multiplication, division, exponentiation, and even more advanced mathematics like estimating trigonometric functions and logarithms, can be surprisingly easy when you know how and practice a little. (most of the courses I know about don't go into the more advanced mathematics, but what makes that easy is the memory aids I mentioned in "Remembering the Numbers". For instance, if you can remember a few values of sines and cosines, you can make reasonably close estimates of other values and, since other logarithmic functions are related to the sine and cosine, you can figure them out easily.)
As per the tradition of "Adventuring", I'm going to resist my desire to teach you how to perform these magical feats and direct you toward the actual magician. Go to your local library, or online or offline bookstore, and get anything by Arthur T. Benjamin - Secrets of Mental Math: The Mathematician's Guide to Lightning Calculation and Amazing Math Tricks, Secrets of Mental Math (a lecture series by The Teaching Company), The Magic of Math: Solving For x and Figuring Out Why, Teach Your Child Math: Making Math Fun for the Both of You.
And if you want to talk about it in more detail, use the blog's comments.
Actually, Mr, Benjamin specializes in combinatorics and has published books in that and other topics of mathematics - but look for his stuff in mental mathematics and (hint, hint) he has a website - https://www.arthurbenjamin.info
Honestly, mathematics can look like magic.