MathGroup Archive 2006

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Errors at discontinuities

  • To: mathgroup at smc.vnet.net
  • Subject: [mg65110] Errors at discontinuities
  • From: "Narasimham" <mathma18 at hotmail.com>
  • Date: Wed, 15 Mar 2006 06:28:22 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

Errors appear at start / period cross-over points of  a triangular wave
on t-axis  with  period a, amplitude b. Why does not
Plot[  D[fn[t,3,4],t]  / D[fn[t,5,5.65],t] , {t, 0,tmax}] ; Or
Plot[  D[fn[t,3,4],t]  , {t, 0,tmax}] ;
work at beginning when the same works erroneously later on in sl1 and
gets self-corrected  at sl2? And how to remedy the situation?  TIA

a= 4 ; b = 3 ; tmax=10;
fn[u_,lam_,A_]=A*ArcSin[Sin[ 2 Pi u/lam]]*2/Pi ;
Plot[ fn[t,a,b], {t, 0,tmax}] ;
Plot[  D[fn[t,a,b],t]  / D[fn[t,c,d],t] , {t, 0,tmax}] ;
sl1=D[fn[t,a,b],t]/D[fn[t,c,d] ] ; Plot[ sl1 ,  {t, 0, tmax}] ;
sl2= D[fn[t,a,b],t]/D[fn[t,c,d],t] ; Plot [sl2, {t, 0, tmax}] ;


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