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From: b3300876@rick.cs.ubc.ca (george kai yee chow)
Newsgroups: comp.sys.handhelds
Subject: Re: Two questions...
Message-ID: <1990Sep26.160424.12956@rick.cs.ubc.ca>
Date: 26 Sep 90 16:04:24 GMT
References: <1990Sep24.183934.575@rick.cs.ubc.ca> <36159@cc.usu.edu>
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Organization: Rick Lab, CPSC, UBC, Vancouver, B.C., Canada
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In article <36159@cc.usu.edu> SLSW2@cc.usu.edu (Roger Ivie) writes:
>In article <1990Sep24.183934.575@rick.cs.ubc.ca>, b3300876@rick.cs.ubc.ca (george kai yee chow) writes:
>> 
>> The second is wrt the cosine function. I was doing some 
>> geometry problem and needed to evaluate cos(pi/3) (I know, I 
>> know, I should know it but I thought I might as well fire up
>> my 48 just for fun). My 48sx returned 0.4999..., not 0.5. 
>> sin(pi/6) does return 0.5 though. Why is this? 
>> 
>One of the more interesting things I encountered when I bought my first
>HP calculator (a 31E) was a long discussion in the manual about this sort
>of problem (I've still got the manual, but it's not handy. If anyone's
>interested, I can find a direct quote).
>
>The gist of the discussion was that since the calculator could not really
>use pi but only a 10-digit approximation of pi, the result of the calculator
>is accurate. It is returning the cosine of precisely that 10-digit
>approximation of (pi/3).

Yes, I'm aware of the problem of calculating with pi. But as I recall reading
in the 48sx's manual, the symbol modes was suppose to elminate that. On the 
48sx, you can ask to keep pi as a symbol to avoid the rounding error.

>===============================================================================
>Roger Ivie
>
>35 S 300 W
>Logan, Ut.  84321
>(801) 752-8633
>===============================================================================

George