38. A rectangle is a parallelogram whoseangles are all right angles, as b {figure above). 39. A rhomboid is an oblique-angled paral-lelogram, as c. Obs.—A triangle which has no right angle is called anoblique triangle. The three angles of a plane triangle, takentogether, are equal to two right…
Design · Decoration and ornament · Art
Internet Archive · Smithsonian Libraries · Public Domain Mark 1.0. Free to use for anything.
![An illustration from Nicolai Copernici Torinensis De reuolutionibus orbium coelestium, libri VI : Habes in hoc opere iam recens nato, & aedito, studiose lector, motus stellarum, tam fixarum, quàm erraticarum, cum ex ueteribus, tum etiam ex recentibus obseruationibus restitutos: & nouis insuper ac admirabilibus hypothesibus ornatos. Habes etiam tabulas expeditissimas, ex quibus eosdem ad quoduis tempus quàm facillime caculare poteris. Igitur eme, lege, fruere. [Line in Greek] (1543)](https://img.insideoutlibrary.com/img/200/ia-nicolaicopernici00cope-56-31.webp)
