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webframp / sicp-info

Stucture and Interpretation of Computer Progams in info format
http://www.neilvandyke.org/sicp-texi/
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Fixed incorrect equation in Ex 2.56. #9

Closed tgvaughan closed 6 years ago

tgvaughan commented 6 years ago

In this TeXinfo version, the first exercise in the symbolic differentiation example incorrectly asks the reader to add the following differentiation rule to the algorithm:

    n_1   n_2
    --- = ---  if and only if n_1 d_2 = n_2 d_1
    d_1   d_2

This is not a differentiation rule and is clearly not the equation that was meant, as is confirmed by referring to the original text of SICP. The rest of the question makes no sense in light of this equation. This PR replaces the equation the correct one:

    d(u^n)             / du \
    ------ = n u^(n-1) | -- |
      dx               \ dx /

It also includes a small typo fix for the build instructions in sicp.el.

webframp commented 6 years ago

I try to avoid altering the original text at all and just repackage so it’s usable in emacs, but I’m ok with this change. Thanks for taking the time!