Path: utzoo!attcan!uunet!samsung!know!sdd.hp.com!hp-pcd!hpcvlx!paulm
From: paulm@hpcvlx.cv.hp.com (Paul J. McClellan)
Newsgroups: comp.sys.handhelds
Subject: Re: Interestring Property of HP-* Calculators
Message-ID: <110540018@hpcvlx.cv.hp.com>
Date: 25 Oct 90 17:20:54 GMT
References: <2821@uc.msc.umn.edu>
Organization: Hewlett-Packard Co., Corvallis, OR, USA
Lines: 38



If you plot the equation 'COS(X)=X' using the HP-28S in degree mode
you will see that a mathematical solution is plausible.  Indeed, one
does exist.  Applying ACOS to both sides of this equation, we obtain
'X=ACOS(X)', which has the same mathematical solution.

Using the HP-28S solver, I obtain the following results in degree mode:

1. Solving 'COS(X)=X' for X with initial guess 1
	=> "Zero"  .999847741531

2. Solving 'ACOS(X)=X' for X with initial guess 1
	=> "Sign Reversal"  .999847741531

These computed results do, indeed, agree.


In radian mode I obtain:

1. Solving 'COS(X)=X' for X with initial guess 1
	=> "Zero"  .739085133215

2. Solving 'ACOS(X)=X' for X with initial guess 1
	=> "Zero"  .739085133215

These computed results also agree.


 +--------------------------------------------------------------------+
 | Paul J. McClellan                 | paulm@cv.hp.com                |
 | Information Technology Operation  | {backbone}!hplabs!hp-pcd!paulm |
 | Hewlett Packard Co.               | (USA) (503) 750-2493  VOICE    |
 | 1000 N.E. Circle Blvd.            | (USA) (503) 750-4980  FAX      |
 | Corvallis, OR   97330             |                                |
 +--------------------------------------------------------------------+
 |                   All relevant disclaimers apply.                  |
 +--------------------------------------------------------------------+