Opened 11 years ago

Closed 9 years ago

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

Reported by: Owned by: mvngu mvngu minor sage-4.8 documentation beginner sd35.5 kcrisman sage-4.8.rc0 Kenneth Smith Karl-Dieter Crisman N/A

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
```

### comment:3 Changed 9 years ago by kcrisman

• Description modified (diff)

### 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:6 follow-up: ↓ 7 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: ↓ 8 Changed 9 years ago by jdemeyer

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
Note: See TracTickets for help on using tickets.