1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
|
(* ========================================================================= *)
(* Examples of using the Grobner basis procedure. *)
(* ========================================================================= *)
time COMPLEX_ARITH
`!a b c.
(a * x pow 2 + b * x + c = Cx(&0)) /\
(a * y pow 2 + b * y + c = Cx(&0)) /\
~(x = y)
==> (a * (x + y) + b = Cx(&0))`;;
time COMPLEX_ARITH
`!a b c.
(a * x pow 2 + b * x + c = Cx(&0)) /\
(Cx(&2) * a * y pow 2 + Cx(&2) * b * y + Cx(&2) * c = Cx(&0)) /\
~(x = y)
==> (a * (x + y) + b = Cx(&0))`;;
(* ------------------------------------------------------------------------- *)
(* Another example. *)
(* ------------------------------------------------------------------------- *)
time COMPLEX_ARITH
`~((y_1 = Cx(&2) * y_3) /\
(y_2 = Cx(&2) * y_4) /\
(y_1 * y_3 = y_2 * y_4) /\
((y_1 pow 2 - y_2 pow 2) * z = Cx(&1)))`;;
time COMPLEX_ARITH
`!y_1 y_2 y_3 y_4.
(y_1 = Cx(&2) * y_3) /\
(y_2 = Cx(&2) * y_4) /\
(y_1 * y_3 = y_2 * y_4)
==> (y_1 pow 2 = y_2 pow 2)`;;
(* ------------------------------------------------------------------------- *)
(* Angle at centre vs. angle at circumference. *)
(* Formulation from "Real quantifier elimination in practice" paper. *)
(* ------------------------------------------------------------------------- *)
time COMPLEX_ARITH
`~((c pow 2 = a pow 2 + b pow 2) /\
(c pow 2 = x0 pow 2 + (y0 - b) pow 2) /\
(y0 * t1 = a + x0) /\
(y0 * t2 = a - x0) /\
((Cx(&1) - t1 * t2) * t = t1 + t2) /\
(u * (b * t - a) = Cx(&1)) /\
(v1 * a + v2 * x0 + v3 * y0 = Cx(&1)))`;;
time COMPLEX_ARITH
`(c pow 2 = a pow 2 + b pow 2) /\
(c pow 2 = x0 pow 2 + (y0 - b) pow 2) /\
(y0 * t1 = a + x0) /\
(y0 * t2 = a - x0) /\
((Cx(&1) - t1 * t2) * t = t1 + t2) /\
(~(a = Cx(&0)) \/ ~(x0 = Cx(&0)) \/ ~(y0 = Cx(&0)))
==> (b * t = a)`;;
time COMPLEX_ARITH
`(c pow 2 = a pow 2 + b pow 2) /\
(c pow 2 = x0 pow 2 + (y0 - b) pow 2) /\
(y0 * t1 = a + x0) /\
(y0 * t2 = a - x0) /\
((Cx(&1) - t1 * t2) * t = t1 + t2) /\
(~(a = Cx(&0)) /\ ~(x0 = Cx(&0)) /\ ~(y0 = Cx(&0)))
==> (b * t = a)`;;
(* ------------------------------------------------------------------------- *)
(* Another example (note we rule out points 1, 2 or 3 coinciding). *)
(* ------------------------------------------------------------------------- *)
time COMPLEX_ARITH
`((x1 - x0) pow 2 + (y1 - y0) pow 2 =
(x2 - x0) pow 2 + (y2 - y0) pow 2) /\
((x2 - x0) pow 2 + (y2 - y0) pow 2 =
(x3 - x0) pow 2 + (y3 - y0) pow 2) /\
((x1 - x0') pow 2 + (y1 - y0') pow 2 =
(x2 - x0') pow 2 + (y2 - y0') pow 2) /\
((x2 - x0') pow 2 + (y2 - y0') pow 2 =
(x3 - x0') pow 2 + (y3 - y0') pow 2) /\
(a12 * (x1 - x2) + b12 * (y1 - y2) = Cx(&1)) /\
(a13 * (x1 - x3) + b13 * (y1 - y3) = Cx(&1)) /\
(a23 * (x2 - x3) + b23 * (y2 - y3) = Cx(&1)) /\
~((x1 - x0) pow 2 + (y1 - y0) pow 2 = Cx(&0))
==> (x0' = x0) /\ (y0' = y0)`;;
time COMPLEX_ARITH
`~(((x1 - x0) pow 2 + (y1 - y0) pow 2 =
(x2 - x0) pow 2 + (y2 - y0) pow 2) /\
((x2 - x0) pow 2 + (y2 - y0) pow 2 =
(x3 - x0) pow 2 + (y3 - y0) pow 2) /\
((x1 - x0') pow 2 + (y1 - y0') pow 2 =
(x2 - x0') pow 2 + (y2 - y0') pow 2) /\
((x2 - x0') pow 2 + (y2 - y0') pow 2 =
(x3 - x0') pow 2 + (y3 - y0') pow 2) /\
(a12 * (x1 - x2) + b12 * (y1 - y2) = Cx(&1)) /\
(a13 * (x1 - x3) + b13 * (y1 - y3) = Cx(&1)) /\
(a23 * (x2 - x3) + b23 * (y2 - y3) = Cx(&1)) /\
(z * (x0' - x0) = Cx(&1)) /\
(z' * (y0' - y0) = Cx(&1)) /\
(z'' * ((x1 - x0) pow 2 + (y1 - y0) pow 2) = Cx(&1)) /\
(z''' * ((x1 - x09) pow 2 + (y1 - y09) pow 2) = Cx(&1)))`;;
(* ------------------------------------------------------------------------- *)
(* These are pure algebraic simplification. *)
(* ------------------------------------------------------------------------- *)
let LAGRANGE_4 = time COMPLEX_ARITH
`(((x1 pow 2) + (x2 pow 2) + (x3 pow 2) + (x4 pow 2)) *
((y1 pow 2) + (y2 pow 2) + (y3 pow 2) + (y4 pow 2))) =
((((((x1*y1) - (x2*y2)) - (x3*y3)) - (x4*y4)) pow 2) +
(((((x1*y2) + (x2*y1)) + (x3*y4)) - (x4*y3)) pow 2) +
(((((x1*y3) - (x2*y4)) + (x3*y1)) + (x4*y2)) pow 2) +
(((((x1*y4) + (x2*y3)) - (x3*y2)) + (x4*y1)) pow 2))`;;
let LAGRANGE_8 = time COMPLEX_ARITH
`((p1 pow 2 + q1 pow 2 + r1 pow 2 + s1 pow 2 + t1 pow 2 + u1 pow 2 + v1 pow 2 + w1 pow 2) *
(p2 pow 2 + q2 pow 2 + r2 pow 2 + s2 pow 2 + t2 pow 2 + u2 pow 2 + v2 pow 2 + w2 pow 2)) =
((p1 * p2 - q1 * q2 - r1 * r2 - s1 * s2 - t1 * t2 - u1 * u2 - v1 * v2 - w1* w2) pow 2 +
(p1 * q2 + q1 * p2 + r1 * s2 - s1 * r2 + t1 * u2 - u1 * t2 - v1 * w2 + w1* v2) pow 2 +
(p1 * r2 - q1 * s2 + r1 * p2 + s1 * q2 + t1 * v2 + u1 * w2 - v1 * t2 - w1* u2) pow 2 +
(p1 * s2 + q1 * r2 - r1 * q2 + s1 * p2 + t1 * w2 - u1 * v2 + v1 * u2 - w1* t2) pow 2 +
(p1 * t2 - q1 * u2 - r1 * v2 - s1 * w2 + t1 * p2 + u1 * q2 + v1 * r2 + w1* s2) pow 2 +
(p1 * u2 + q1 * t2 - r1 * w2 + s1 * v2 - t1 * q2 + u1 * p2 - v1 * s2 + w1* r2) pow 2 +
(p1 * v2 + q1 * w2 + r1 * t2 - s1 * u2 - t1 * r2 + u1 * s2 + v1 * p2 - w1* q2) pow 2 +
(p1 * w2 - q1 * v2 + r1 * u2 + s1 * t2 - t1 * s2 - u1 * r2 + v1 * q2 + w1* p2) pow 2)`;;
let LIOUVILLE = time COMPLEX_ARITH
`((x1 pow 2 + x2 pow 2 + x3 pow 2 + x4 pow 2) pow 2) =
(Cx(&1 / &6) * ((x1 + x2) pow 4 + (x1 + x3) pow 4 + (x1 + x4) pow 4 +
(x2 + x3) pow 4 + (x2 + x4) pow 4 + (x3 + x4) pow 4) +
Cx(&1 / &6) * ((x1 - x2) pow 4 + (x1 - x3) pow 4 + (x1 - x4) pow 4 +
(x2 - x3) pow 4 + (x2 - x4) pow 4 + (x3 - x4) pow 4))`;;
let FLECK = time COMPLEX_ARITH
`((x1 pow 2 + x2 pow 2 + x3 pow 2 + x4 pow 2) pow 3) =
(Cx(&1 / &60) * ((x1 + x2 + x3) pow 6 + (x1 + x2 - x3) pow 6 +
(x1 - x2 + x3) pow 6 + (x1 - x2 - x3) pow 6 +
(x1 + x2 + x4) pow 6 + (x1 + x2 - x4) pow 6 +
(x1 - x2 + x4) pow 6 + (x1 - x2 - x4) pow 6 +
(x1 + x3 + x4) pow 6 + (x1 + x3 - x4) pow 6 +
(x1 - x3 + x4) pow 6 + (x1 - x3 - x4) pow 6 +
(x2 + x3 + x4) pow 6 + (x2 + x3 - x4) pow 6 +
(x2 - x3 + x4) pow 6 + (x2 - x3 - x4) pow 6) +
Cx(&1 / &30) * ((x1 + x2) pow 6 + (x1 - x2) pow 6 +
(x1 + x3) pow 6 + (x1 - x3) pow 6 +
(x1 + x4) pow 6 + (x1 - x4) pow 6 +
(x2 + x3) pow 6 + (x2 - x3) pow 6 +
(x2 + x4) pow 6 + (x2 - x4) pow 6 +
(x3 + x4) pow 6 + (x3 - x4) pow 6) +
Cx(&3 / &5) * (x1 pow 6 + x2 pow 6 + x3 pow 6 + x4 pow 6))`;;
let HURWITZ = time COMPLEX_ARITH
`!x1 x2 x3 x4.
(x1 pow 2 + x2 pow 2 + x3 pow 2 + x4 pow 2) pow 4 =
Cx(&1 / &840) * ((x1 + x2 + x3 + x4) pow 8 +
(x1 + x2 + x3 - x4) pow 8 +
(x1 + x2 - x3 + x4) pow 8 +
(x1 + x2 - x3 - x4) pow 8 +
(x1 - x2 + x3 + x4) pow 8 +
(x1 - x2 + x3 - x4) pow 8 +
(x1 - x2 - x3 + x4) pow 8 +
(x1 - x2 - x3 - x4) pow 8) +
Cx(&1 / &5040) * ((Cx(&2) * x1 + x2 + x3) pow 8 +
(Cx(&2) * x1 + x2 - x3) pow 8 +
(Cx(&2) * x1 - x2 + x3) pow 8 +
(Cx(&2) * x1 - x2 - x3) pow 8 +
(Cx(&2) * x1 + x2 + x4) pow 8 +
(Cx(&2) * x1 + x2 - x4) pow 8 +
(Cx(&2) * x1 - x2 + x4) pow 8 +
(Cx(&2) * x1 - x2 - x4) pow 8 +
(Cx(&2) * x1 + x3 + x4) pow 8 +
(Cx(&2) * x1 + x3 - x4) pow 8 +
(Cx(&2) * x1 - x3 + x4) pow 8 +
(Cx(&2) * x1 - x3 - x4) pow 8 +
(Cx(&2) * x2 + x3 + x4) pow 8 +
(Cx(&2) * x2 + x3 - x4) pow 8 +
(Cx(&2) * x2 - x3 + x4) pow 8 +
(Cx(&2) * x2 - x3 - x4) pow 8 +
(x1 + Cx(&2) * x2 + x3) pow 8 +
(x1 + Cx(&2) * x2 - x3) pow 8 +
(x1 - Cx(&2) * x2 + x3) pow 8 +
(x1 - Cx(&2) * x2 - x3) pow 8 +
(x1 + Cx(&2) * x2 + x4) pow 8 +
(x1 + Cx(&2) * x2 - x4) pow 8 +
(x1 - Cx(&2) * x2 + x4) pow 8 +
(x1 - Cx(&2) * x2 - x4) pow 8 +
(x1 + Cx(&2) * x3 + x4) pow 8 +
(x1 + Cx(&2) * x3 - x4) pow 8 +
(x1 - Cx(&2) * x3 + x4) pow 8 +
(x1 - Cx(&2) * x3 - x4) pow 8 +
(x2 + Cx(&2) * x3 + x4) pow 8 +
(x2 + Cx(&2) * x3 - x4) pow 8 +
(x2 - Cx(&2) * x3 + x4) pow 8 +
(x2 - Cx(&2) * x3 - x4) pow 8 +
(x1 + x2 + Cx(&2) * x3) pow 8 +
(x1 + x2 - Cx(&2) * x3) pow 8 +
(x1 - x2 + Cx(&2) * x3) pow 8 +
(x1 - x2 - Cx(&2) * x3) pow 8 +
(x1 + x2 + Cx(&2) * x4) pow 8 +
(x1 + x2 - Cx(&2) * x4) pow 8 +
(x1 - x2 + Cx(&2) * x4) pow 8 +
(x1 - x2 - Cx(&2) * x4) pow 8 +
(x1 + x3 + Cx(&2) * x4) pow 8 +
(x1 + x3 - Cx(&2) * x4) pow 8 +
(x1 - x3 + Cx(&2) * x4) pow 8 +
(x1 - x3 - Cx(&2) * x4) pow 8 +
(x2 + x3 + Cx(&2) * x4) pow 8 +
(x2 + x3 - Cx(&2) * x4) pow 8 +
(x2 - x3 + Cx(&2) * x4) pow 8 +
(x2 - x3 - Cx(&2) * x4) pow 8) +
Cx(&1 / &84) * ((x1 + x2) pow 8 + (x1 - x2) pow 8 +
(x1 + x3) pow 8 + (x1 - x3) pow 8 +
(x1 + x4) pow 8 + (x1 - x4) pow 8 +
(x2 + x3) pow 8 + (x2 - x3) pow 8 +
(x2 + x4) pow 8 + (x2 - x4) pow 8 +
(x3 + x4) pow 8 + (x3 - x4) pow 8) +
Cx(&1 / &840) * ((Cx(&2) * x1) pow 8 + (Cx(&2) * x2) pow 8 +
(Cx(&2) * x3) pow 8 + (Cx(&2) * x4) pow 8)`;;
let SCHUR = time COMPLEX_ARITH
`Cx(&22680) * (x1 pow 2 + x2 pow 2 + x3 pow 2 + x4 pow 2) pow 5 =
Cx(&9) * ((Cx(&2) * x1) pow 10 +
(Cx(&2) * x2) pow 10 +
(Cx(&2) * x3) pow 10 +
(Cx(&2) * x4) pow 10) +
Cx(&180) * ((x1 + x2) pow 10 + (x1 - x2) pow 10 +
(x1 + x3) pow 10 + (x1 - x3) pow 10 +
(x1 + x4) pow 10 + (x1 - x4) pow 10 +
(x2 + x3) pow 10 + (x2 - x3) pow 10 +
(x2 + x4) pow 10 + (x2 - x4) pow 10 +
(x3 + x4) pow 10 + (x3 - x4) pow 10) +
((Cx(&2) * x1 + x2 + x3) pow 10 +
(Cx(&2) * x1 + x2 - x3) pow 10 +
(Cx(&2) * x1 - x2 + x3) pow 10 +
(Cx(&2) * x1 - x2 - x3) pow 10 +
(Cx(&2) * x1 + x2 + x4) pow 10 +
(Cx(&2) * x1 + x2 - x4) pow 10 +
(Cx(&2) * x1 - x2 + x4) pow 10 +
(Cx(&2) * x1 - x2 - x4) pow 10 +
(Cx(&2) * x1 + x3 + x4) pow 10 +
(Cx(&2) * x1 + x3 - x4) pow 10 +
(Cx(&2) * x1 - x3 + x4) pow 10 +
(Cx(&2) * x1 - x3 - x4) pow 10 +
(Cx(&2) * x2 + x3 + x4) pow 10 +
(Cx(&2) * x2 + x3 - x4) pow 10 +
(Cx(&2) * x2 - x3 + x4) pow 10 +
(Cx(&2) * x2 - x3 - x4) pow 10 +
(x1 + Cx(&2) * x2 + x3) pow 10 +
(x1 + Cx(&2) * x2 - x3) pow 10 +
(x1 - Cx(&2) * x2 + x3) pow 10 +
(x1 - Cx(&2) * x2 - x3) pow 10 +
(x1 + Cx(&2) * x2 + x4) pow 10 +
(x1 + Cx(&2) * x2 - x4) pow 10 +
(x1 - Cx(&2) * x2 + x4) pow 10 +
(x1 - Cx(&2) * x2 - x4) pow 10 +
(x1 + Cx(&2) * x3 + x4) pow 10 +
(x1 + Cx(&2) * x3 - x4) pow 10 +
(x1 - Cx(&2) * x3 + x4) pow 10 +
(x1 - Cx(&2) * x3 - x4) pow 10 +
(x2 + Cx(&2) * x3 + x4) pow 10 +
(x2 + Cx(&2) * x3 - x4) pow 10 +
(x2 - Cx(&2) * x3 + x4) pow 10 +
(x2 - Cx(&2) * x3 - x4) pow 10 +
(x1 + x2 + Cx(&2) * x3) pow 10 +
(x1 + x2 - Cx(&2) * x3) pow 10 +
(x1 - x2 + Cx(&2) * x3) pow 10 +
(x1 - x2 - Cx(&2) * x3) pow 10 +
(x1 + x2 + Cx(&2) * x4) pow 10 +
(x1 + x2 - Cx(&2) * x4) pow 10 +
(x1 - x2 + Cx(&2) * x4) pow 10 +
(x1 - x2 - Cx(&2) * x4) pow 10 +
(x1 + x3 + Cx(&2) * x4) pow 10 +
(x1 + x3 - Cx(&2) * x4) pow 10 +
(x1 - x3 + Cx(&2) * x4) pow 10 +
(x1 - x3 - Cx(&2) * x4) pow 10 +
(x2 + x3 + Cx(&2) * x4) pow 10 +
(x2 + x3 - Cx(&2) * x4) pow 10 +
(x2 - x3 + Cx(&2) * x4) pow 10 +
(x2 - x3 - Cx(&2) * x4) pow 10) +
Cx(&9) * ((x1 + x2 + x3 + x4) pow 10 +
(x1 + x2 + x3 - x4) pow 10 +
(x1 + x2 - x3 + x4) pow 10 +
(x1 + x2 - x3 - x4) pow 10 +
(x1 - x2 + x3 + x4) pow 10 +
(x1 - x2 + x3 - x4) pow 10 +
(x1 - x2 - x3 + x4) pow 10 +
(x1 - x2 - x3 - x4) pow 10)`;;
(* ------------------------------------------------------------------------- *)
(* Intersection of diagonals of a parallelogram is their midpoint. *)
(* Kapur "...Dixon resultants, Groebner Bases, and Characteristic Sets", 3.1 *)
(* ------------------------------------------------------------------------- *)
time COMPLEX_ARITH
`(x1 = u3) /\
(x1 * (u2 - u1) = x2 * u3) /\
(x4 * (x2 - u1) = x1 * (x3 - u1)) /\
(x3 * u3 = x4 * u2) /\
~(u1 = Cx(&0)) /\
~(u3 = Cx(&0))
==> (x3 pow 2 + x4 pow 2 = (u2 - x3) pow 2 + (u3 - x4) pow 2)`;;
(* ------------------------------------------------------------------------- *)
(* Chou's formulation of same property. *)
(* ------------------------------------------------------------------------- *)
time COMPLEX_ARITH
`(u1 * x1 - u1 * u3 = Cx(&0)) /\
(u3 * x2 - (u2 - u1) * x1 = Cx(&0)) /\
(x1 * x4 - (x2 - u1) * x3 - u1 * x1 = Cx(&0)) /\
(u3 * x4 - u2 * x3 = Cx(&0)) /\
~(u1 = Cx(&0)) /\
~(u3 = Cx(&0))
==> (Cx(&2) * u2 * x4 + Cx(&2) * u3 * x3 - u3 pow 2 - u2 pow 2 = Cx(&0))`;;
(* ------------------------------------------------------------------------- *)
(* Perpendicular lines property; from Kapur's earlier paper. *)
(* ------------------------------------------------------------------------- *)
time COMPLEX_ARITH
`(y1 * y3 + x1 * x3 = Cx(&0)) /\
(y3 * (y2 - y3) + (x2 - x3) * x3 = Cx(&0)) /\
~(x3 = Cx(&0)) /\
~(y3 = Cx(&0))
==> (y1 * (x2 - x3) = x1 * (y2 - y3))`;;
(* ------------------------------------------------------------------------- *)
(* Simson's theorem (Chou, p7). *)
(* ------------------------------------------------------------------------- *)
time COMPLEX_ARITH
`(Cx(&2) * u2 * x2 + Cx(&2) * u3 * x1 - u3 pow 2 - u2 pow 2 = Cx(&0)) /\
(Cx(&2) * u1 * x2 - u1 pow 2 = Cx(&0)) /\
(--(x3 pow 2) + Cx(&2) * x2 * x3 + Cx(&2) * u4 * x1 - u4 pow 2 = Cx(&0)) /\
(u3 * x5 + (--u2 + u1) * x4 - u1 * u3 = Cx(&0)) /\
((u2 - u1) * x5 + u3 * x4 + (--u2 + u1) * x3 - u3 * u4 = Cx(&0)) /\
(u3 * x7 - u2 * x6 = Cx(&0)) /\
(u2 * x7 + u3 * x6 - u2 * x3 - u3 * u4 = Cx(&0)) /\
~(Cx(&4) * u1 * u3 = Cx(&0)) /\
~(Cx(&2) * u1 = Cx(&0)) /\
~(--(u3 pow 2) - u2 pow 2 + Cx(&2) * u1 * u2 - u1 pow 2 = Cx(&0)) /\
~(u3 = Cx(&0)) /\
~(--(u3 pow 2) - u2 pow 2 = Cx(&0)) /\
~(u2 = Cx(&0))
==> (x4 * x7 + (--x5 + x3) * x6 - x3 * x4 = Cx(&0))`;;
(* ------------------------------------------------------------------------- *)
(* Determinants from Coq convex hull paper (some require reals or order). *)
(* ------------------------------------------------------------------------- *)
let det3 = new_definition
`det3(a11,a12,a13,
a21,a22,a23,
a31,a32,a33) =
a11 * (a22 * a33 - a32 * a23) -
a12 * (a21 * a33 - a31 * a23) +
a13 * (a21 * a32 - a31 * a22)`;;
let DET_TRANSPOSE = prove
(`det3(a1,b1,c1,a2,b2,c2,a3,b3,c3) =
det3(a1,a2,a3,b1,b2,b3,c1,c2,c3)`,
REWRITE_TAC[det3] THEN CONV_TAC(time COMPLEX_ARITH));;
let sdet3 = new_definition
`sdet3(p,q,r) = det3(FST p,SND p,Cx(&1),
FST q,SND q,Cx(&1),
FST r,SND r,Cx(&1))`;;
let SDET3_PERMUTE_1 = prove
(`sdet3(p,q,r) = sdet3(q,r,p)`,
REWRITE_TAC[sdet3; det3] THEN CONV_TAC(time COMPLEX_ARITH));;
let SDET3_PERMUTE_2 = prove
(`sdet3(p,q,r) = --(sdet3(p,r,q))`,
REWRITE_TAC[sdet3; det3] THEN CONV_TAC(time COMPLEX_ARITH));;
let SDET_SUM = prove
(`sdet3(p,q,r) - sdet3(t,q,r) - sdet3(p,t,r) - sdet3(p,q,t) = Cx(&0)`,
REWRITE_TAC[sdet3; det3] THEN CONV_TAC(time COMPLEX_ARITH));;
let SDET_CRAMER = prove
(`sdet3(s,t,q) * sdet3(t,p,r) = sdet3(t,q,r) * sdet3(s,t,p) +
sdet3(t,p,q) * sdet3(s,t,r)`,
REWRITE_TAC[sdet3; det3] THEN CONV_TAC(time COMPLEX_ARITH));;
let SDET_NZ = prove
(`!p q r. ~(sdet3(p,q,r) = Cx(&0))
==> ~(p = q) /\ ~(q = r) /\ ~(r = p)`,
REWRITE_TAC[FORALL_PAIR_THM; PAIR_EQ; sdet3; det3] THEN
CONV_TAC(time COMPLEX_ARITH));;
let SDET_LINCOMB = prove
(`(FST p * sdet3(i,j,k) =
FST i * sdet3(j,k,p) + FST j * sdet3(k,i,p) + FST k * sdet3(i,j,p)) /\
(SND p * sdet3(i,j,k) =
SND i * sdet3(j,k,p) + SND j * sdet3(k,i,p) + SND k * sdet3(i,j,p))`,
REWRITE_TAC[sdet3; det3] THEN CONV_TAC(time COMPLEX_ARITH));;
(***** I'm not sure if this is true; there must be some
sufficient degenerate conditions....
let th = prove
(`~(~(xp pow 2 + yp pow 2 = Cx(&0)) /\
~(xq pow 2 + yq pow 2 = Cx(&0)) /\
~(xr pow 2 + yr pow 2 = Cx(&0)) /\
(det3(xp,yp,Cx(&1),
xq,yq,Cx(&1),
xr,yr,Cx(&1)) = Cx(&0)) /\
(det3(yp,xp pow 2 + yp pow 2,Cx(&1),
yq,xq pow 2 + yq pow 2,Cx(&1),
yr,xr pow 2 + yr pow 2,Cx(&1)) = Cx(&0)) /\
(det3(xp,xp pow 2 + yp pow 2,Cx(&1),
xq,xq pow 2 + yq pow 2,Cx(&1),
xr,xr pow 2 + yr pow 2,Cx(&1)) = Cx(&0)))`,
REWRITE_TAC[det3] THEN
CONV_TAC(time COMPLEX_ARITH));;
***************)
(* ------------------------------------------------------------------------- *)
(* Some geometry concepts (just "axiomatic" in this file). *)
(* ------------------------------------------------------------------------- *)
prioritize_real();;
let collinear = new_definition
`collinear (a:real#real) b c <=>
((FST a - FST b) * (SND b - SND c) =
(SND a - SND b) * (FST b - FST c))`;;
let parallel = new_definition
`parallel (a,b) (c,d) <=>
((FST a - FST b) * (SND c - SND d) = (SND a - SND b) * (FST c - FST d))`;;
let perpendicular = new_definition
`perpendicular (a,b) (c,d) <=>
((FST a - FST b) * (FST c - FST d) + (SND a - SND b) * (SND c - SND d) =
&0)`;;
let oncircle_with_diagonal = new_definition
`oncircle_with_diagonal a (b,c) = perpendicular (b,a) (c,a)`;;
let length = new_definition
`length (a,b) = sqrt((FST a - FST b) pow 2 + (SND a - SND b) pow 2)`;;
let lengths_eq = new_definition
`lengths_eq (a,b) (c,d) <=>
((FST a - FST b) pow 2 + (SND a - SND b) pow 2 =
(FST c - FST d) pow 2 + (SND c - SND d) pow 2)`;;
let is_midpoint = new_definition
`is_midpoint b (a,c) <=>
(&2 * FST b = FST a + FST c) /\
(&2 * SND b = SND a + SND c)`;;
(* ------------------------------------------------------------------------- *)
(* Chou isn't explicit about this. *)
(* ------------------------------------------------------------------------- *)
let is_intersection = new_definition
`is_intersection p (a,b) (c,d) <=>
collinear a p b /\ collinear c p d`;;
(* ------------------------------------------------------------------------- *)
(* This is used in some degenerate conditions. See Chou, p18. *)
(* ------------------------------------------------------------------------- *)
let isotropic = new_definition
`isotropic (a,b) = perpendicular (a,b) (a,b)`;;
(* ------------------------------------------------------------------------- *)
(* This increases degree, but sometimes makes complex assertion useful. *)
(* ------------------------------------------------------------------------- *)
let distinctpairs = new_definition
`distinctpairs pprs <=>
~(ITLIST (\(a,b) pr. ((FST a - FST b) pow 2 + (SND a - SND b) pow 2) * pr)
pprs (&1) = &0)`;;
(* ------------------------------------------------------------------------- *)
(* Simple tactic to remove defined concepts and expand coordinates. *)
(* ------------------------------------------------------------------------- *)
let (EXPAND_COORDS_TAC:tactic) =
let complex2_ty = `:real#real` in
fun (asl,w) ->
(let fvs = filter (fun v -> type_of v = complex2_ty) (frees w) in
MAP_EVERY (fun v -> SPEC_TAC(v,v)) fvs THEN
GEN_REWRITE_TAC DEPTH_CONV [FORALL_PAIR_THM; EXISTS_PAIR_THM] THEN
REPEAT GEN_TAC) (asl,w);;
let PAIR_BETA_THM = prove
(`(\(x,y). P x y) (a,b) = P a b`,
CONV_TAC(LAND_CONV GEN_BETA_CONV) THEN REFL_TAC);;
let GEOM_TAC =
EXPAND_COORDS_TAC THEN
GEN_REWRITE_TAC TOP_DEPTH_CONV
[collinear; parallel; perpendicular; oncircle_with_diagonal;
length; lengths_eq; is_midpoint; is_intersection; distinctpairs;
isotropic; ITLIST; PAIR_BETA_THM; BETA_THM; PAIR_EQ; FST; SND];;
(* ------------------------------------------------------------------------- *)
(* Centroid (Chou, example 142). *)
(* ------------------------------------------------------------------------- *)
let CENTROID = time prove
(`is_midpoint d (b,c) /\
is_midpoint e (a,c) /\
is_midpoint f (a,b) /\
is_intersection m (b,e) (a,d)
==> collinear c f m`,
GEOM_TAC THEN CONV_TAC GROBNER_REAL_ARITH);;
(* ------------------------------------------------------------------------- *)
(* Gauss's theorem (Chou, example 15). *)
(* ------------------------------------------------------------------------- *)
let GAUSS = time prove
(`collinear x a0 a3 /\
collinear x a1 a2 /\
collinear y a2 a3 /\
collinear y a1 a0 /\
is_midpoint m1 (a1,a3) /\
is_midpoint m2 (a0,a2) /\
is_midpoint m3 (x,y)
==> collinear m1 m2 m3`,
GEOM_TAC THEN CONV_TAC GROBNER_REAL_ARITH);;
(* ------------------------------------------------------------------------- *)
(* Simson's theorem (Chou, example 288). *)
(* ------------------------------------------------------------------------- *)
(**** These are all hideously slow. At least the first one works.
I haven't had the patience to try the rest.
let SIMSON = time prove
(`lengths_eq (O,a) (O,b) /\
lengths_eq (O,a) (O,c) /\
lengths_eq (d,O) (O,a) /\
perpendicular (e,d) (b,c) /\
collinear e b c /\
perpendicular (f,d) (a,c) /\
collinear f a c /\
perpendicular (g,d) (a,b) /\
collinear g a b /\
~(collinear a c b) /\
~(lengths_eq (a,b) (a,a)) /\
~(lengths_eq (a,c) (a,a)) /\
~(lengths_eq (b,c) (a,a))
==> collinear e f g`,
GEOM_TAC THEN CONV_TAC GROBNER_REAL_ARITH);;
let SIMSON = time prove
(`lengths_eq (O,a) (O,b) /\
lengths_eq (O,a) (O,c) /\
lengths_eq (d,O) (O,a) /\
perpendicular (e,d) (b,c) /\
collinear e b c /\
perpendicular (f,d) (a,c) /\
collinear f a c /\
perpendicular (g,d) (a,b) /\
collinear g a b /\
~(a = b) /\ ~(a = c) /\ ~(a = d) /\ ~(b = c) /\ ~(b = d) /\ ~(c = d)
==> collinear e f g`,
GEOM_TAC THEN CONV_TAC GROBNER_REAL_ARITH);;
let SIMSON = time prove
(`lengths_eq (O,a) (O,b) /\
lengths_eq (O,a) (O,c) /\
lengths_eq (d,O) (O,a) /\
perpendicular (e,d) (b,c) /\
collinear e b c /\
perpendicular (f,d) (a,c) /\
collinear f a c /\
perpendicular (g,d) (a,b) /\
collinear g a b /\
~(collinear a c b) /\
~(isotropic (a,b)) /\
~(isotropic (a,c)) /\
~(isotropic (b,c)) /\
~(isotropic (a,d)) /\
~(isotropic (b,d)) /\
~(isotropic (c,d))
==> collinear e f g`,
GEOM_TAC THEN CONV_TAC GROBNER_REAL_ARITH);;
****************)
|
