What is MathML?
Updated:
MathML is the XML language for mathematical notation, allowed inside EPUB 3 content documents so equations stay text instead of images. Support in reading apps varies.
Why it matters when you convert a PDF to EPUB
A PDF draws an equation as positioned glyphs and lines, with no record of its structure. Rebuilding MathML from that is hard; a converter that cannot do it reliably should keep the equation's text in order rather than produce wrong mathematics. EPUBCheck asks MathML to carry alternative text (ACC-009).
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