Here is the title page of Part I of the General Trattato di Numeri (General Treatise on Number and Measure) (1556) of Nicolo Tartaglia (1500-1557). This is an extensive work on elementary mathematics that was popular in Italy for several decades after its publication.
Here is folio 29 of the General Treatise. Here Tartaglia is showing how to determine the area of an irregular curved shape.