Yes, my friends and relatives think I'm crazy, but this is what I do....
Recently, in the comments to my post
Pythagorean Triples: An Easier Way, blogger
Keith issued a friendly challenge involving primitive triples with the same hypotenuse.
I have to be honest here: it never occurred to me that two primitive triples would have the same hypotenuse for two reasons: first, I hadn't really looked at numbers that went that high (and I'm certainly not using them in class); second, they didn't fit my three models for Pythagorean Triples:
a, b, b+1; a, b, b+2; and
a, a+1, c.
I explained why
b+3 didn't work, but I never pondered if
b+9 or
b+18 would work. And, I know now, it would have.
Basically, I wanted to investigate this myself, just for fun. So I didn't use the formulas I knew about, namely pick an m and n and calculate
a=m2-n2, b=2mn, and
c=m2+n2.
That will give you every triple there is, primitive or not, with lots of repeats, in a very disorganized manner. (For one thing,
b will always be the
even number, not the
middle number.)
But since I didn't use it, and despite the graphic I generated in this
comic, I omitted the following triples from my original
list of Pythagorean Triples (3-50):
33, 56, 65 and 36, 77, 85This, of course, got me to wondering why some hypotenuses would have more than one. Well, that's kind of obvious, depending on whose lists of numbers you look at. But, of course, I'm more interested in seeing if there's any pattern to be found.
In the meantime, here's an updated list:
Pythagorean triples, sorted by the shortest side, from 3 to 50.
Leg | Primitive | Non-Primitive |
3 | 3,4,5 | -- |
4 | -- | -- |
5 | 5,12,13 | -- |
6 | -- | 6,8,10 |
7 | 7,24,25 | -- |
8 | 8,15,17 | -- |
9 | 9,40,41 | 9,12,15 |
10 | -- | 10,24,26 |
11 | 11,60,61 | -- |
12 | 12,35,37 | 12,16,20 |
13 | 13,84,85 | -- |
14 | -- | 14,48,50 |
15 | 15,112,113 | 15,20,25; 15,36,39 |
16 | 16,63,65 | 16,30,34 |
17 | 17,144,145 | -- |
18 | -- | 18,24,30; 18,80,82 |
19 | 19,180,181 | -- |
20 | 20,99,101; 20,21,29 | 20,48,52 |
21 | 21,220,221 | 21,28,35; 21,72,75 |
22 | -- | 22,120,122 |
23 | 23,264,265 | -- |
24 | 24,143,145 | 24,32,40; 24,45,51; 24,70,74 |
25 | 25,312,313 | 25,60,65 |
26 | -- | 26,168,170 |
27 | 27,364,365 | 27,36,45; 27,120,123 |
28 | 28,195,197 | 28,96,100 |
29 | 29,420,421 | -- |
30 | -- | 30,40,50; 30,72,78; 30,224,226 |
31 | 31,480,481 | -- |
32 | 32,255,257 | 32,60,68; 32,126,130 |
33 | 33,56,65; 33,544,545 | 33,44,55; 33,180,183 |
34 | -- | 34,288,290 |
35 | 35,612,613 | 35,84,91; 35,120,125 |
36 | 36,77,85; 36,323,325 | 36,48,60; 36,160,164; 36,105,111 |
37 | 37,684,685 | -- |
38 | -- | 38,360,362 |
39 | 39,760,761 | 39,42,65; 39,252,255 |
40 | 40,399,401 | 40,96,104; 40,75,85; 40,198,202; 40,42,58 |
41 | 41,840,841 | -- |
42 | -- | 42,56,70; 42,144,150 |
43 | 43,924,925 | -- |
44 | 44,483,485 | 44,240,244 |
45 | 45,1012,1013 | 45,60,75; 45,108,117; 45,200,205;45,336,339 |
46 | -- | 46,528,530 |
47 | 47,1104,1105 | -- |
48 | 48,575,577 | 48,64,80; 48,90,102; 48,140,148;48,286,290 |
49 | 49,1200,1201 | 49,168,175 |
50 | -- | 50,120,130; 50,624,626 |