355f2001_recur

# 355f2001_recur - Linear Recurrence Relations in Maple Date:...

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Linear Recurrence Relations in Maple Date: Nov 7, 2001 Last Revision: Nov 15, 2001 Maple 6 Bent E. Petersen [email protected] [email protected] Course: Mth 355 (a.k.a. Mth 399) Term: Fall 2001 File name: 355f2001_recur.mws Assignment 6 (problems at end) - due Nov 14, 2001. This worksheet contains a few comments on some of Maple’s recurrence relations support. It composed fairly quickly and is unlikely to be free of errors. If you find a serious error be sure to mention it in your solution report. > restart; Let’s load the plots package - just in case. > with(plots): Warning, the name changecoords has been redefined Example 1 The Maple function rsolve() is used to solve linear recurrence relations. Here is an example of an order 2 recurrence relation with initial conditions. > eqn1:=a(n)=a(n-1)+a(n-2); # Fibonacci := eqn1 = () a n + a n 1( ) a n 2 > init1:=a(0)=0,a(1)=1; := init1 , = a0 0 = a1 1 To solve we throw all the equations into one set and also specify for which variable to solve. > soln1:=rsolve({eqn1,init1},a);

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:= soln1 + 1 5 51 2 1 1 5 n 1 5 1 5 2 1 + 1 5 n + 1 5 That’s all there is to it! This expression is not in the usual Binet form, so you may want to try to get Maple to cast it in a more familiar form. Good luck! We can also use rsolve() to find the generating function for the solution. Note the single quotes surrounding genfunc in the following command. > gen1:=rsolve({eqn1,init1},a,’genfunc’(z)); := gen1 z − + + 1 zz 2 We can even define a procedure which will compute the a(n). > fun1:=rsolve({eqn1,init1},a,’makeproc’): The fun1() procedure can be use to plot the sequence a(n) > sq1:=seq([n,fun1(n)],n=0. .16); sq1 [] , 00 [ ] , 11 [ ] , 21 [ ] , 32 [ ] , 43 [ ] , 55 [ ] , 68 [ ] , 71 3 [ ] , 82 1 [ ] , 93 4 [ ] , 10 55 ,,,,,,, , , , , := , 11 89 [ ] , 12 144 [ ] , 13 233 [ ] , 14 377 [ ] , 15 610 [ ] , 16 987 ,,,,, > PLOT(POINTS(sq1),SYMBOL(BOX,16),TEXT([5,1000],"fun1 - Fibonacci sequence"));
We could plot a curve instead > PLOT(CURVES([sq1]),TEXT([5,900],"fun1 - Fibonacci sequence"));

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Here’s one (kludgy) way to get the characteristic polynomial and the characteristic root > subs(a(n)=x^n,a(n-1)=x^(n-1),a(n-2)=x^(n-2),eqn1)/x^(n-2): cpoly1:=simplify(%); := cpoly1 = x 2 + x 1 > croot1:=solve(cpoly1,x); := croot1 , + 1 2 1 2 5 1 2 1 2 5
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## This note was uploaded on 02/11/2012 for the course MTH 141, 142, taught by Professor Mcallister during the Spring '08 term at SUNY Empire State.

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355f2001_recur - Linear Recurrence Relations in Maple Date:...

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