tan(pi/2)=195948537906 (?)

06092020, 09:25 AM
Post: #1




tan(pi/2)=195948537906 (?)
This is discovered by a colleague of mine.
From the Home screen tan(pi/6) gives 0.577.. and pressing [a b/c] gives a nice sqrt(1/3) tan(pi/2) is giving 195948537906 Surely, Prime could do better than that, e.g. "Error: x/0" or "Math error"? Version: 2020 01 21 

06092020, 09:36 AM
Post: #2




RE: tan(pi/2)=195948537906 (?)
Well, that IS the correct answer for tan(1.5707963268)...
I don't know the Prime, but I gather the same difference applies as in the 49G and up: the difference between numeric pi and symbolic 'PI'. The former is a 12digit approximation, the latter the real thing. Werner 

06092020, 10:04 AM
Post: #3




RE: tan(pi/2)=195948537906 (?)  
06092020, 11:22 AM
Post: #4




RE: tan(pi/2)=195948537906 (?)
TI84 CET (v5.4.0.0034)
returns an error tan(pi/2) = Error I'd prefer an error over the misleading answer that is the result of underlying approximations. My guess is that TI and other calculators recognize the special condition and bypass the approximate calculation and issue a predefined result. (I'm not into CAS as of yet) 

06092020, 01:25 PM
Post: #5




RE: tan(pi/2)=195948537906 (?)
I'm afraid it's the TI's answer that is misleading...
try tan(5*pi/2) or so. Werner 

06092020, 01:51 PM
Post: #6




RE: tan(pi/2)=195948537906 (?)
HP15C > 4878048780
HP35s > 195948537906 HP49g+: 195948537906 (or infinite symbol if CAS / Approx is unchecked) Free42 (iOS): 1,79243... E33 WP34s (iOS): 1,6149... E15 It's a resolutely numerical approach. Quote:I'm not into CAS as of yetYou should not dissociate the CAS from the rest of the Prime, especially if you're looking for symbolic computation such as TAN(PI/2) > infinite. 

06092020, 02:06 PM
Post: #7




RE: tan(pi/2)=195948537906 (?)  
06092020, 03:13 PM
Post: #8




RE: tan(pi/2)=195948537906 (?)
(06092020 11:22 AM)StephanP Wrote: I'd prefer an error over the misleading answer that is the result of underlying approximations. What if you want the tan of 1.5707963268? Now who has the misleading answer? 

06092020, 04:30 PM
(This post was last modified: 06092020 04:32 PM by Joe Horn.)
Post: #9




RE: tan(pi/2)=195948537906 (?)
(06092020 01:51 PM)pinkman Wrote: HP15C > 4878048780 HP's philosophy is very different from other calculator manufacturers: "Our users know what they're doing and know how to use the tool in their hand. The numbers that they input to any function are exactly what they intended to input, to the last digit. We do the same with the output. We show ALL the digits. We don't cheat by hiding several digits behind the euphemism of 'guard digits'. So if a user presses the PI key, we assume that the user knows that the result is not the infinite number of digits of pi, nor is it a result whose last few digits are a secret. The user is smart enough to know that pressing PI on an HP 12digitmantissa machine yields exactly 3.14159265359, no more and no less. If the user then divides by 2 and then presses the TAN key in radian mode, we assume that the user wants the tangent of exactly the number of radians in the display, and we return all the digits of the result rounded to 12 significant digits. On HP calculators, what you see is exactly what you have." TI's philosophy is, "We assume that the user is an idiot who thinks that pressing the PI key actually returns exactly pi. Furthermore, if they then divide it by 2 and take the TAN in radian mode, we catch that particular case and we ASSUME that we know better than the user does, and we return what WE think that the user PROBABLY expects. We also display fewer digits than are calculated, hiding the roundoff errors behind 'guard digits' so that nobody is confused when they get nasty EXACT results like HP gives." It's not a matter of who is right or which philosophy is better. It's a matter of knowing how your tools work and using them accordingly. <0ɸ0> Joe 

06092020, 05:39 PM
Post: #10




RE: tan(pi/2)=195948537906 (?)
[quote='pinkman' pid='132979' dateline='1591710691']
Free42 (iOS): 1,79243... E33 WP34s (iOS): 1,6149... E15 [quote] On my actual WP34S in doubleprecision mode, I get 1.792 431 373 312 990 354 164 577 572 292 315 E33 Jake 

06092020, 06:35 PM
Post: #11




RE: tan(pi/2)=195948537906 (?)
Yes I was in Double mode off. Same result when toggling Double on.


06092020, 07:56 PM
Post: #12




RE: tan(pi/2)=195948537906 (?)
(06092020 09:25 AM)StephanP Wrote: tan(pi/2) is giving 195948537906It's also helpful to put this into perspective. Suppose you stood up a tower that leaned with this slope (195,948,537,906). How tall would the tower be if it was outofplumb by 1 foot at the base? The answer is it would have to reach almost to Mars.... 

06092020, 09:28 PM
Post: #13




RE: tan(pi/2)=195948537906 (?)
Interestingly, if you go back to the HP45 and TI30, it appears the HP fudges it, but the TI doesn't!
HP 45: Pi/2 = 1.570796327 tan(Pi/2) = 9.999999999E99 (the overflow display on the HP45) TI 30: Pi/2 = 1.5707963268 tan(Pi/2) = 1.8312E09 tan(1.570796327) = 2.9298E09 (using the HP version of Pi/2) 

06102020, 05:33 AM
Post: #14




RE: tan(pi/2)=195948537906 (?)
Hello,
Thanks Joe, I could not have said it (because I need to stay diplomatic In some ways, this is why there is a CAS mode and a num mode on Prime. num (home) is to do numerical calculations. calculations with number where a number is a number... cas is to do symbolic calculations, where variables and math concepts are being worked on. You want tan(PI/2) to be undefined? this is cas world, you want real number crunching, this is home mode... I find it EXTREMLY frustrating when I am in the workshop, grab one of the kids (junior high school calc) calculator (they were forced to get some other brand!!!) try to find the hypothenuse of a triangle to cut a chunk of wood, and the thing returns some symbolic expression... I mean, my ruler does not have any marking at square root (50)! I want 7.07! Prime, at the touch of a button will let you do the calculations in whatever domain you want. And I find it great. Cyrille Although I work for the HP calculator group, the views and opinions I post here are my own. I do not speak for HP. 

06102020, 07:40 PM
Post: #15




RE: tan(pi/2)=195948537906 (?)
(06102020 05:33 AM)cyrille de brébisson Wrote: Hello, Don't your kids calcs have an approx mode? Esben 28s, 35s, 49G+, 50G, Elektronika MK52 & MK61 

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