[spec] add formula for length of a parametric curve

diff --git a/chem/reactions.pdf b/chem/reactions.pdf
index 8419a6e06f7aa2dbf9dacb8c91eb77916fc42491..83780ebd665f26ca20b60c2e92ded695d1b996d2 100644 (file)
Binary files a/chem/reactions.pdf and b/chem/reactions.pdf differ