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MathGroup Archive 1996

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errors in 3.0(beta) and 2.2

  • To: mathgroup at smc.vnet.net
  • Subject: [mg5604] errors in 3.0(beta) and 2.2
  • From: Jonathan Connor <Jonathan.Connor at nessie.mcc.ac.uk>
  • Date: Fri, 27 Dec 1996 01:59:10 -0500
  • Sender: owner-wri-mathgroup at wolfram.com

(* It is very easy to get completely wrong results
in both 2.2 and 3.0(beta) using one line examples. 
The following example concerns LegendreP[10,10,x] 
in 2.2 on a Mac, but I got similar results with
3.0(beta). I noticed the errors when using Plot[]
with LegendreP[10,10,Cos[t*Degree]]
	I would appreciate comments, workarounds etc. 
Does the released version of 3.0 have these errors?

$Version
Macintosh 2.2 (May 4, 1993)

(* Notice LegendreP[10,10,x] is a simple polynomial 
of degree 10 *)

LegendreP[10,10,x]
                  2       4       6      8    10
654729075 (1 - 5 x  + 10 x  - 10 x  + 5 x  - x  )

(*The following two results look reasonable *)
LegendreP[10,10,Cos[179*Degree]]//N
          -9
2.27155 10
LegendreP[10,10,Cos[t*Degree]]/.t->179.0//N
          -9
2.27155 10

(* The next result is wrong *)
LegendreP[10,10,Cos[179.0*Degree]]//N
          8
1.02775 10

(* All the following results are wrong *)
LegendreP[10,10,Cos[179.9999*Degree]]//N
           48
-2.68317 10
LegendreP[10,10,Cos[179.99999*Degree]]//N
          51
4.88061 10
LegendreP[10,10,Cos[179.999999*Degree]]//N
          57
4.87838 10
LegendreP[10,10,Cos[t*Degree]]/.t->179.999999//N
0


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