The elements of Euclid for the use of schools and colleges; comprising the first six books and portions of the eleventh and twelfth books; (1903)
Euclid, Todhunter, I. (Isaac), 1820-1884, ed. edt, Simson, Robert, 1687-1768, ed. edt · London; New York, Macmillan · leaf 316
L 9. .*. the angles ABG and BGH together = two right angles. [L 29. Also the angle BGH has been shewn to be a right angle; .-. the Z.ABG is a right l.For the same reason the Z.CBG is a right L]; .•. GB is perpendicular to the plane through AB, BC. [XL 4.|,And GB is also _L^ to the plane through DE,… … If two parallel planes be cut by another plane, their commonsections with it are parallel Let the parallel planes AB, CD be cut by the plane EFHG,and let their common sections with itbe EF, GH:EF shall be parallel to GH. Construction. For if not, EF andGH, being produced, will meet eithertowards F,…
Euclid's Elements · Geometry · Mathematics, Greek
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