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42 sito, si per tres angulos, singule recte linee ponantur [[superscript]] b [[/superscript]] stantes [[superscript]] a [[/superscript]] heque tres inclinentur ^ [[insertion]] ut [[/insertion]] ad unum medium punctum uertices uingant, fit piramis, que cum a triangula basi profecta sit tribus angulis per latera concludatur, hoc modo. Sit .a b c. triangulum. Si huic igitur triangulo, per tres angulos erigantur linee, et ad unum punctum conuertantur, qui est .d. ita ut est .d. punctum, non sit in plano, sed pendens ille scilicet linee ad ipse erecte, uerticem et quodammodo cacumen .d. facient, et erit basis .a b c. unum triangulum, per laterea uero triangula ^ [[insertion]] tria [[/insertion]] id est unum triangulum .a d c. aliud uero .b d c. Tertium uero .b d a. ut manifestat hec forma. [[red ink]] De piramidis que a quadratis uel a ceteris multi angulis proficiscuntur - [[/red ink]] [[large red capital I with blue penwork]]Tem si a tetragona basi proficiscatur, et ad unum uerticem eius linee dirigantur, erit piramis quatuor triangulorum per latera, uno tamen tetragono in basi posito, super quam figura ipsa fundata est. Et si a pentagono surgant quinque linee, rursus piramis quinque triangulis continebitur. Et si ab exagono, sex triangulis, et nihilo minus. Et quantos angulos habuerit figura super quam piramis residet, tot ipsa per latera, triangulis continetur, ut ex subiectis descriptionibus palam est. [[image: red five-sided pyramid drawn from above, labelled underneath]] Pentagonus [[image: red six-sided pyramid drawn from above, labelled underneath]] Exagonus [[image: red seven-sided pyramid drawn from above, labelled underneath]] Eptagonus [[red paragraphus]] Dicitur autem huius piramides, hoc modo. Prima piramis, de [[margin]] [[image: red eight-sided pyramid drawn from above, labelled underneath]] octogonus [[/margin]] [[image: red four-sided pyramid drawn from above, labelled underneath]] tetragonus
