COS(X) dislpay wrong answer

[Magnus512]

(09-02-2018 12:10 PM)Albert Chan Wrote:  

(09-02-2018 03:40 AM)Magnus512 Wrote:  When I run the operation that give me that result outside the function ---> x:=r*COS(θ); I get 2 as answer.
In CAS in home I get 1.9999999... So even If I write the decimal point the answer must be 2. or 1,

When you say result outside the function, I assume you meant do it on a regular calculator.

Example, on my Casio FX-115MS, COS(1 + .0471975512) = 0.5, so X = 4 * 0.5 = 2.0

Prime had a bit more precision: 12 BCD digits in home, 48-bits binary float in CAS
This is the result of COS(1.0471975512):

Home => COS(10471975512/1E10) = 0.499999999997
C A S => COS(0x1.0c152382daf4) = 0x1.fffffffff30aP-2 ~ 0.49999999999705

Thus, X = 1.9999999 ...
But, if you round X to 10 digits, you get 2.0, same as my Casio

BTW, I do not have a Prime, above numbers based on specs I read from thread HP Prime Miscalculating

By outside the function I mean in CAS and home view directly, in home view I get the rounding error in cas I don't get that error. I'm not talking about other calculators here.
So maybe I have to activate the fixed or rounded mode in the program... Sucks