A quick precision test
06-06-2014, 12:57 AM
Post: #52
 Claudio L. Senior Member Posts: 1,847 Joined: Dec 2013
RE: A quick precision test
(06-05-2014 10:09 PM)Paul Dale Wrote:
(06-05-2014 09:08 PM)Claudio L. Wrote:  I've also checked with Wolfram Alpha, and... exact same number! (I checked up to 36 digits only, the others are left to the reader to compare...)

When I do this on Wolfram Alpha, which is usually my gold standard for accuracy I get the numbers I quoted. This is the query I used.

Quote:hint: Alpha won't give you more than the number of digits you input, so it will show only 5 digits unless you add lots of trailing zeros to the input argument.

It will if you ask for them

- Pauli

Huh? The result given by alpha is different if you ask "with 72 decimal digits" or if you add 36 trailing zeroes to the number.
I just did:
COS(1.57079632679489661923132169163975144) with 72 decimal digits
(I didn't know you could write that in "human words", that's cool! if it only gave good answers...)
And I also did
COS(1.57079632679489661923132169163975144000000000000000000000000000000000000) (36 zeroes, for a total of 72 decimal digits, so it should be the same...right?)

The result in each case is:
2.098584699687552910487393316601323231×10^-36
2.09858469968755291048747229615390820 × 10^-36

What's going on? is it making the digits up or what? The second answer agrees with newRPL and preccalc, which is why I "conveniently" choose to believe that one. I say "conveniently" because it agrees with my code, not because I know it for a fact to be correct.

I used to trust the results from Alpha blindly (and from the past few posts, I can tell you too). Now I just don't know what to believe, and neither should you from now on.

Claudio
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 Messages In This Thread A quick precision test - pito - 06-02-2014, 10:37 PM RE: A quick precison test - Paul Dale - 06-02-2014, 11:04 PM RE: A quick precison test - pito - 06-03-2014, 12:07 AM RE: A quick precison test - Paul Dale - 06-03-2014, 12:13 AM RE: A quick precison test - pito - 06-03-2014, 12:27 AM RE: A quick precison test - Paul Dale - 06-03-2014, 12:36 AM RE: A quick precision test - Claudio L. - 06-04-2014, 01:25 PM RE: A quick precision test - walter b - 06-04-2014, 01:33 PM RE: A quick precision test - Claudio L. - 06-04-2014, 01:42 PM RE: A quick precision test - Paul Dale - 06-04-2014, 09:47 PM RE: A quick precison test - Gerson W. Barbosa - 06-03-2014, 01:51 AM RE: A quick precison test - Massimo Gnerucci - 06-03-2014, 06:21 AM RE: A quick precison test - walter b - 06-03-2014, 11:24 AM RE: A quick precison test - Massimo Gnerucci - 06-03-2014, 11:31 AM RE: A quick precision test - Gerson W. Barbosa - 06-03-2014, 10:20 PM RE: A quick precision test - Didier Lachieze - 06-03-2014, 10:38 PM RE: A quick precision test - Gerson W. Barbosa - 06-04-2014, 05:07 AM RE: A quick precision test - Dieter - 06-04-2014, 01:08 PM RE: A quick precision test - walter b - 06-04-2014, 01:23 PM RE: A quick precison test - HP67 - 06-03-2014, 09:06 AM RE: A quick precison test - Massimo Gnerucci - 06-03-2014, 09:15 AM RE: A quick precision test - everettr - 06-03-2014, 02:11 PM RE: A quick precision test - Gerson W. Barbosa - 06-03-2014, 09:39 PM RE: A quick precision test - Massimo Gnerucci - 06-03-2014, 10:06 PM RE: A quick precision test - Gerson W. Barbosa - 06-08-2014, 02:10 AM RE: A quick precison test - pito - 06-03-2014, 07:23 AM RE: A quick precison test - HP67 - 06-03-2014, 11:50 AM RE: A quick precison test - Paul Dale - 06-03-2014, 12:25 PM RE: A quick precision test - Massimo Gnerucci - 06-03-2014, 12:57 PM RE: A quick precision test - walter b - 06-03-2014, 01:52 PM RE: A quick precision test - Paul Dale - 06-03-2014, 10:10 PM RE: A quick precison test - HP67 - 06-03-2014, 12:41 PM RE: A quick precision test - HP67 - 06-03-2014, 01:01 PM RE: A quick precision test - walter b - 06-03-2014, 01:56 PM RE: A quick precision test - pito - 06-04-2014, 01:38 PM RE: A quick precision test - Claudio L. - 06-04-2014, 02:17 PM RE: A quick precision test - Paul Dale - 06-04-2014, 10:09 PM RE: A quick precision test - Claudio L. - 06-05-2014, 01:18 AM RE: A quick precision test - Paul Dale - 06-05-2014, 02:00 AM RE: A quick precision test - Claudio L. - 06-05-2014, 11:03 AM RE: A quick precision test - Dieter - 06-05-2014, 11:23 AM RE: A quick precision test - Paul Dale - 06-05-2014, 12:06 PM RE: A quick precision test - Claudio L. - 06-05-2014, 09:08 PM RE: A quick precision test - Paul Dale - 06-05-2014, 10:09 PM RE: A quick precision test - Claudio L. - 06-06-2014 12:57 AM RE: A quick precision test - Claudio L. - 06-06-2014, 01:15 AM RE: A quick precision test - Paul Dale - 06-06-2014, 01:35 AM RE: A quick precision test - pito - 06-06-2014, 11:16 AM RE: A quick precision test - Claudio L. - 06-06-2014, 12:04 PM RE: A quick precision test - Paul Dale - 06-06-2014, 10:55 PM RE: A quick precision test - pito - 06-07-2014, 11:56 AM RE: A quick precision test - Paul Dale - 06-07-2014, 12:20 PM RE: A quick precision test - pito - 06-07-2014, 04:44 PM RE: A quick precision test - walter b - 06-08-2014, 05:28 PM RE: A quick precision test - Claudio L. - 06-05-2014, 09:25 PM RE: A quick precision test - Paul Dale - 06-05-2014, 10:20 PM RE: A quick precision test - Claudio L. - 06-06-2014, 01:03 AM RE: A quick precision test - Paul Dale - 06-06-2014, 01:46 AM RE: A quick precision test - pito - 06-04-2014, 02:12 PM RE: A quick precision test - pito - 06-04-2014, 02:31 PM RE: A quick precision test - pito - 06-05-2014, 08:49 PM RE: A quick precision test - walter b - 06-05-2014, 09:07 PM RE: A quick precision test - pito - 06-05-2014, 09:13 PM RE: A quick precision test - Mark Hardman - 06-05-2014, 09:21 PM RE: A quick precision test - pito - 06-06-2014, 12:19 PM RE: A quick precision test - pito - 06-08-2014, 12:44 PM RE: A quick precision test - walter b - 06-08-2014, 01:57 PM RE: A quick precision test - pito - 06-08-2014, 02:07 PM RE: A quick precision test - walter b - 06-08-2014, 03:00 PM RE: A quick precision test - Paul Dale - 06-08-2014, 10:46 PM