Celestial scenery, or, The Wonders of the planetary system displayed : illustrating the perfections of deity and a plurality of worlds (1845)
Dick, Thomas, 1774-1857, Parker, E. S., former owner. DSI, David H. DeVorkin Collection (Smithsonian Institution. Libraries) DSI · Philadelphia : Published by Edward C. Biddle · leaf 297
e or half a right angle, it is said tobe an angle of forty-five degrees. A triangle is a figurewhich contains three angles and three sides, as O P Q, FigCIV. It is demonstrated by mathematicians, that the threeangles of every triangle, whatever proportion these anglesmay bear to each other, are… … O and P, are together equal to ninety degrees ; so that, if oneof these angles be known, the other is found by subtractingthe number of degrees in the known angle from ninety. Thus,if the angle at P be equal to thirty degrees, the angle at Owill be equal to sixty degrees. Hence, if any two angles…
Astronomy
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