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Sin sum (Posted on 2020-12-11) Difficulty: 3 of 5
Let x be the sum of the values of sin(n) for the whole numbers 0 though n. (In radians, of course.)

Find the maximum A and minimum B such that

A < x < B


Adapted from AMS Page A Day Calendar by Evelyn Lamb December 7.

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Max and Min biased, but constant difference between | Comment 2 of 14 |
The difference between max and min is more fundamental than the actual values of the two:

The positive side, for the max, has the advantage of going first and thus biasing toward a higher max and min:

      i   sin(i)      x
      0  0.000000  0.000000
      1  0.841471  0.841471
      2  0.909297  1.750768
      3  0.141120  1.891888
      4 -0.756802  1.135086
      5 -0.958924  0.176162
      6 -0.279415 -0.103254
      7  0.656987  0.553733
      8  0.989358  1.543091
      9  0.412118  1.955209
     10 -0.544021  1.411188
     11 -0.999990  0.411198
     12 -0.536573 -0.125375
     13  0.420167  0.294792
     
and subsequent samples then reflect this bias;     
     
    100 -0.506366 -0.127171
    101  0.452026  0.324855
    102  0.994827  1.319682
    103  0.622989  1.942670
    104 -0.321622  1.621048
    105 -0.970535  0.650513
    106 -0.727143 -0.076630
    107  0.184782  0.108152
    108  0.926819  1.034970
    109  0.816743  1.851713
    110 -0.044243  1.807470
    111 -0.864551  0.942919
    112 -0.889996  0.052923
    113 -0.097182 -0.044259
    
    200 -0.873297  0.032700
    201 -0.061890 -0.029191
    202  0.806418  0.777228
    203  0.933310  1.710538
    204  0.202120  1.912658
    205 -0.714898  1.197760
    206 -0.974642  0.223118
    207 -0.338305 -0.115187
    208  0.609068  0.493881
    209  0.996467  1.490348
    210  0.467719  1.958067
    211 -0.491048  1.467019
    212 -0.998347  0.468672
    213 -0.587771 -0.119099
    
    300 -0.999756  0.435590
    301 -0.558764 -0.123174
    302  0.395953  0.272779
    303  0.986633  1.259411
    304  0.670207  1.929618
    305 -0.262404  1.667214
    306 -0.953762  0.713452
    307 -0.768235 -0.054783
    308  0.123603  0.068820
    309  0.901801  0.970621
    310  0.850888  1.821509
    311  0.017672  1.839181
    312 -0.831791  1.007389
    313 -0.916509  0.090880
    
    400 -0.850919  0.970558
    401 -0.901775  0.068783
    402 -0.123543 -0.054760
    403  0.768274  0.713514
    404  0.953744  1.667257
    405  0.262346  1.929603
    406 -0.670252  1.259352
    407 -0.986623  0.272729
    408 -0.395897 -0.123168
    409  0.558814  0.435646
    410  0.999755  1.435400
    411  0.521525  1.956925
    412 -0.436192  1.520733
    413 -0.992876  0.527857
    
    500 -0.467772  1.490296
    501 -0.996472  0.493824
    502 -0.609020 -0.115196
    503  0.338362  0.223166
    504  0.974655  1.197821
    505  0.714855  1.912676
    506 -0.202179  1.710497
    507 -0.933331  0.777166
    508 -0.806383 -0.029217
    509  0.061950  0.032733
    510  0.873327  0.906060
    511  0.881770  1.787830
    512  0.079518  1.867349
    513 -0.795842  1.071506
    
    600  0.044182  1.851685
    601 -0.816777  1.034908
    602 -0.926796  0.108112
    603 -0.184722 -0.076611
    604  0.727184  0.650573
    605  0.970521  1.621094
    606  0.321565  1.942659
    607 -0.623036  1.319624
    608 -0.994821  0.324803
    609 -0.451972 -0.127169
    610  0.506418  0.379249
    611  0.999209  1.378458
    612  0.573332  1.951790
    613 -0.379664  1.572127
    
    700  0.543971  1.955214
    701 -0.412173  1.543041
    702 -0.989367  0.553674
    703 -0.656941 -0.103267
    704  0.279473  0.176206
    705  0.958941  1.135147
    706  0.756763  1.891910
    707 -0.141180  1.750731
    708 -0.909323  0.841408
    709 -0.841438 -0.000030
    710  0.000060  0.000030
    711  0.841504  0.841534
    712  0.909272  1.750806
    713  0.141060  1.891866
    
    800  0.893970  1.772375
    801  0.105928  1.878302
    802 -0.779504  1.098798
    803 -0.948263  0.150535
    804 -0.245194 -0.094658
    805  0.683306  0.588648
    806  0.983577  1.572224
    807  0.379552  1.951776
    808 -0.573431  1.378345
    809 -0.999204  0.379141
    810 -0.506314 -0.127173
    811  0.452080  0.324907
    812  0.994833  1.319740
    813  0.622941  1.942681
    
    900  0.997803  1.353514
    901  0.594860  1.948374
    902 -0.354995  1.593379
    903 -0.978469  0.614910
    904 -0.702343 -0.087433
    905  0.219513  0.132080
    906  0.939551  1.071631
    907  0.795769  1.867400
    908 -0.079639  1.787761
    909 -0.881827  0.905934
    910 -0.873268  0.032666
    911 -0.061830 -0.029164
    912  0.806454  0.777290
    913  0.933288  1.710578
    
After 100 million trials (n=100,000,000), the maximum reached was 1.95815868232315 and the minimum -0.127670960610926 for a difference of 2.08582964293407.

The closeness of the difference to 2 can be attributed to the average number of samples in a positive or negative grouping being pi (approximately, as only a finite, though large, number of samples were taken) and the area of a lobe of the sine curve being 2.

Not knowing how much farther we'd have to go to get the asymptotic value if the difference (or the actual max and min), I'd just quote the difference as being approximately 2.08583, though, if we start at 3 radians rather than zero, we do get max = 0.207390270689346 min= -1.87843937224483 for a difference of 2.08582964293417, so it looks close. And starting with i=2 radians, max= 1.11668769751522  min=   -0.969141945418661 difference = 2.08582964293388.

Final answer: difference is approximately 2.08582964293.

Addendum: Starting with i=2.2, to get a different set of numbers altogether, the difference is reported as 2.08582964697012, so perhaps 2.0858296 is a better approximation, showing that less precision is deserved.

Theoretical consideration: As pi is irrational the difference between the max and min should approach the same value, although the actual min and max values would be different based on the head start provided by where you start on the sine curve.

max=0; min=30; t=0;
for i= 0:100000000
   t=t+sin(i);
   if i<1000 
       if mod(i,100)<14
        fprintf('%7d %9.6f %9.6f\n',i,sin(i),t)
       end
   end
   if t>max
       max=t;
   end
   if t<min
       min=t;
   end  
end
disp([max min max-min])


  Posted by Charlie on 2020-12-11 10:40:21
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