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From: hoford@sequoia.upenn.edu (John Hoford)
Newsgroups: comp.sys.handhelds
Subject: Re: A strange feature (a bug?)
Keywords: symbolic integration/differentation in DEG mode
Message-ID: <30902@netnews.upenn.edu>
Date: 10 Oct 90 14:11:46 GMT
References: <1990Oct10.093506.8848@wuarchive.wustl.edu>
Sender: news@netnews.upenn.edu
Organization: CIRC,Radiology,U. of Pennsylvania
Lines: 23

In article <1990Oct10.093506.8848@wuarchive.wustl.edu> hp48sx@wuarchive.wustl.edu (HP48SX Archive Maintainer) writes:

>If I try to evaluate dX(sin(X)) then I get:
>cos(x)*(dX(X)*(pi/180))
>/* if the factor pi/180 should be applied, then it should be multiplied
>   to the x in cox(x), but even this is not correct */
>further EVAL gives:
>cos(X)*(pi/180)
>
>As it looks like the hp48 is only capable of giving the correct results
>in radians mode, the HP should have ensured that


sin(x) in deg.    =  sin(x*(pi/180)) in rad.
since dx(sin(x)) = cos(x) is true for rad.


dx(sin(x(pi/180))) = cos(x)(pi/180)
using the rule  dx(f(g(x))) = (dx(f(x)))*(dx(g(x)))

It is not a bug it is math

John D. Hoford