(If you find that the solutions are too numerous, choose the solutions which provide the smallest perimeter and area.)
Source: Original.
Sides of triangle = a b c
Sides of rectangle = x y
Let j = (a+b+c)/2 (1)
Let k = sqrt[j(j-a)(j-b)(j-c)] (2)
Since a+b+c = 2(x+y), then j=x+y (3)
Since xy = (2), then xy = k (4)
Combining (3) and (4):
j - y = k / y ; y^2 - jy + k = 0
Then: y = [j +- sqrt(j^2 - 4k)] / 2 (quadratic)
This equation permits a reasonable a b c loop;
I kept my sides lesser than 100;
most "economical" loop (I think):
Loop a from 2 to 98
Loop b from a to 99
If even(a) then s = b else s = b + 1 (s = start with)
f = a + b -1 (f = finish with)
If f > 99 then f = 99
Loop c from s to f incrementing c by 2 **
...go to work!
** this is made possible due to the "s" calculation;
also results in a+b+c being even at all times.
And this gives 5 "natives" (all sides < 100):
a b c x y perimeters areas
5 5 6 2 6 16 12
13 20 21 6 21 54 126
25 51 52 12 52 128 624
53 53 56 21 60 162 1260
68 87 95 30 95 250 2850
BUT I didn't like the fact that in every case, there are at
least 2 sides equal; so to add some dignity to this puzzle,
I looked for the cases where NONE of the 5 sides were equal.
And I found 10 "natives" (all sides < 500):
a b c x y perimeters areas
37 130 157 12 150 324 1800
63 298 325 28 315 686 8820
81 113 130 36 126 324 4536
110 261 349 30 330 720 9900
132 265 353 45 330 750 14850
145 174 221 60 210 540 12600
149 245 390 14 378 784 5292
164 195 281 60 260 640 15600
175 208 303 63 280 686 17640
195 259 314 84 300 768 25200
684 745 821 285 840 2250 239400 **
** in case someone wants the highest
"a" case, where all sides < 1000 !!
The following is a solution for any positive integer m: (2m^2+2m+1, m^3+2m^2+2m, m^3+2m^2+2m+1) = (m^2+m, m^3+2m^2+2m+1) Notation: If a triangle with sides (a, b, c) and a rectangle with sides (x, y) are a solution, we'll write (a, b, c) = (x, y). If (a, b, c) = (x, y) is a solution, then we can form an infinite number of solutions by "scaling up" by any integral factor m. That is, (ma, mb, mc) = (mx, my) is also a solution. Let's call any solution which cannot be derived by scaling up a "primitive" solution. This is a list of all primitive solutions with perimeter less than 2500, listed in order of increasing perimeter: (5, 5, 6) = (2, 6), P = 16, A = 12 (13, 20, 21) = (6, 21), P = 54, A = 126 (25, 51, 52) = (12, 52), P = 128, A = 624 (53, 53, 56) = (21, 60), P = 162, A = 1260 (68, 87, 95) = (30, 95), P = 250, A = 2850 (41, 104, 105) = (20, 105), P = 250, A = 2100 (81, 113, 130) = (36, 126), P = 324, A = 4536 (37, 130, 157) = (12, 150), P = 324, A = 1800 (61, 185, 186) = (30, 186), P = 432, A = 5580 (145, 174, 221) = (60, 210), P = 540, A = 12600 (164, 195, 281) = (60, 260), P = 640, A = 15600 (195, 232, 259) = (84, 259), P = 686, A = 21756 (148, 265, 273) = (70, 273), P = 686, A = 19110 (85, 300, 301) = (42, 301), P = 686, A = 12642 (175, 208, 303) = (63, 280), P = 686, A = 17640 (63, 298, 325) = (28, 315), P = 686, A = 8820 (110, 261, 349) = (30, 330), P = 720, A = 9900 (132, 265, 353) = (45, 330), P = 750, A = 14850 (195, 259, 314) = (84, 300), P = 768, A = 25200 (149, 245, 390) = (14, 378), P = 784, A = 5292 (267, 365, 392) = (120, 392), P = 1024, A = 47040 (113, 455, 456) = (56, 456), P = 1024, A = 25536 (287, 401, 562) = (105, 520), P = 1250, A = 54600 (157, 481, 612) = (40, 585), P = 1250, A = 23400 (265, 471, 544) = (120, 520), P = 1280, A = 62400 (189, 500, 661) = (45, 630), P = 1350, A = 28350 (424, 485, 549) = (180, 549), P = 1458, A = 98820 (260, 595, 603) = (126, 603), P = 1458, A = 75978 (145, 656, 657) = (72, 657), P = 1458, A = 47304 (113, 630, 715) = (36, 693), P = 1458, A = 24948 (296, 625, 679) = (140, 660), P = 1600, A = 92400 (532, 533, 685) = (210, 665), P = 1750, A = 139650 (447, 763, 790) = (210, 790), P = 2000, A = 165900 (181, 909, 910) = (90, 910), P = 2000, A = 81900 (493, 565, 942) = (130, 870), P = 2000, A = 113100 (661, 663, 724) = (264, 760), P = 2048, A = 200640 (157, 916, 975) = (72, 952), P = 2048, A = 68544 (500, 543, 1015) = (63, 966), P = 2058, A = 60858 (684, 745, 821) = (285, 840), P = 2250, A = 239400