A treatise on surveying and navigation: uniting the theoretical, practical, and educational features of these subjects (1857)
Robinson, Horatio N[elson], 1806-1867. [from old catalog] · Cincinnati, J. Ernst; Toledo, Anderson, Burr, & co. · leaf 18
PROBLEM 9. To find a fourth proportional to three given lines. Let AB, AC, AD, represent the A three given lines. Place the first twotogether, at a point forming any angle,as BAC, and join BC. On AB placeAD, and from the point D, draw(problem 6) DE parallel to BC; AEwill be the fourth proportional… … PROBLEM 10. To find the middle, or mean proportional, between two given lines. Place AB and BC in one right line,and, on AC, as a diameter, describe asemicircle (postulate 3), and from thepoint B, draw BD at right angles to A C(problem 3); BD is the mean propor-tional required. Proof, (scholium to…
Surveying · Navigation
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