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

[sagetrac-mvngu]

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 

CC: @kcrisman

Component: documentation

Keywords: beginner sd35.5

Author: Kenneth Smith

Reviewer: Karl-Dieter Crisman

Merged: sage-4.8.rc0

Issue created by migration from https://trac.sagemath.org/ticket/8245

[sagetrac-ksmith]

Author: Kenneth Smith

[sagetrac-ksmith]

comment:4

Attachment: trac_8245_Euler_Guided_Tour.patch.gz

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

[sagetrac-ksmith]

Changed keywords from none to beginner sd35.5

[kcrisman]

Reviewer: Karl-Dieter Crisman

[kcrisman]

comment:6

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.

[jdemeyer]

comment:7

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.

[kcrisman]

comment:8

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.

[jdemeyer]

Merged: sage-4.8.rc0