Opened 11 years ago

Closed 9 years ago

#8245 closed defect (fixed)

tutorial: typo in section "Euler’s Method for Systems of Differential Equations"

Reported by: mvngu Owned by: mvngu
Priority: minor Milestone: sage-4.8
Component: documentation Keywords: beginner sd35.5
Cc: kcrisman Merged in: sage-4.8.rc0
Authors: Kenneth Smith Reviewers: Karl-Dieter Crisman
Report Upstream: N/A Work issues:
Branch: Commit:
Dependencies: Stopgaps:

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Description (last modified by kcrisman)

From sage-support:

In the section, "A Guided Tour"->"Basic Algebra and Calculus"-
>"Euler’s Method for Systems of Differential Equations", I found that

the answer of the example is z(1)≈0.75, which seems to be wrong.

The calculation is
------------------------------------------------------------------------
sage: t,x,y = PolynomialRing(RealField(10),3,"txy").gens()
sage: f = y; g = -x - y * t
sage: eulers_method_2x2(f,g, 0, 1, 0, 1/4, 1)
         t                    x                h*f(t,x,y)                    y           h*g(t,x,y)
         0                    1                      0.00                    0                -0.25
       1/4                  1.0                    -0.062                -0.25                -0.23
       1/2                 0.94                     -0.12                -0.48                -0.17
       3/4                 0.82                     -0.16                -0.66               -0.081
         1                 0.65                     -0.18                -0.74                0.022
------------------------------------------------------------------------

So I think the right answer should be z(1)≈0.65 

Attachments (1)

trac_8245_Euler_Guided_Tour.patch (829 bytes) - added by ksmith 9 years ago.

Download all attachments as: .zip

Change History (10)

comment:1 Changed 11 years ago by jason

  • Keywords beginner added

comment:2 Changed 10 years ago by kcrisman

  • Cc kcrisman added

comment:3 Changed 9 years ago by kcrisman

  • Description modified (diff)

Changed 9 years ago by ksmith

comment:4 Changed 9 years ago by ksmith

  • Authors set to Kenneth Smith
  • Status changed from new to needs_review

I just made that one change making the 7 a 6.

comment:5 Changed 9 years ago by ksmith

  • Keywords sd35.5 added

comment:6 follow-up: Changed 9 years ago by kcrisman

  • Reviewers set to Karl-Dieter Crisman
  • Status changed from needs_review to positive_review

And the math turns out to be right. The example itself is somewhat elliptically expressed, but this is fine.

Curious as to why we have both :math: and the backticks... but anyway, that would be a general overhaul of the tutorial.

comment:7 in reply to: ↑ 6 ; follow-up: Changed 9 years ago by jdemeyer

Replying to kcrisman:

Curious as to why we have both :math: and the backticks... but anyway, that would be a general overhaul of the tutorial.

Within Sage, `foo` is equivalent to :math:`foo`. In general ReST code, this is not true.

comment:8 in reply to: ↑ 7 Changed 9 years ago by kcrisman

Curious as to why we have both :math: and the backticks... but anyway, that would be a general overhaul of the tutorial.

Within Sage, `foo` is equivalent to :math:`foo`. In general ReST code, this is not true.

Ah, so it's historical in that sense. Thanks for the clarification.

comment:9 Changed 9 years ago by jdemeyer

  • Merged in set to sage-4.8.rc0
  • Resolution set to fixed
  • Status changed from positive_review to closed
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