Mattison, Hiram, 1811-1868 · New York, Huntington and Savage, Mason and Law · leaf 22
lel planes.] 34. When are Planes said to bePerpendicular 1 When one stands exactly up-right upon the other; or whenthey cut each other at rightangles. [In the figure one plane is placed horizontally,and the other perpendicular to it. They aretherefore perpendicular to each other, howeverthey may… … * A plane surface is to be distinguished from a pic 16 PRIMARY ASTRONOMY. ANGLE OF INCLINATION.
Astronomy
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