Practical navigation, or, An introduction to the whole art : containing the doctrine of plain and spherical triangles : plain, mercator, great-circle sailing, and astronomical problems : the use of divers instruments ... : sundry useful tables in navigation, and a table of 10,000 logarithms, and of the logarithm-sines, tangents, and secants / by John Seller.

  • Seller, John, active 1658-1698.
Date:
1694
Catalogue details

Licence: Public Domain Mark

Credit: Practical navigation, or, An introduction to the whole art : containing the doctrine of plain and spherical triangles : plain, mercator, great-circle sailing, and astronomical problems : the use of divers instruments ... : sundry useful tables in navigation, and a table of 10,000 logarithms, and of the logarithm-sines, tangents, and secants / by John Seller. Source: Wellcome Collection.

    52/532 (page 38)
    SS a ee aes —— SS ‘ an ws Se CHAP. IV. Tbe. DoGrine of Spherical T x1anctes, SECT. (1. , | Containing the Affettions of Spherical Triangles, and | | their Axioms. | te Spherical Triangle is that which is defcribed on the Surface of the Sphere, | Te 2. ‘The Sides of a Spherical Triangle are the Arches of 4s. ot. three great Circles: of the Sphere mutually interfecting each other. 3. Spherical Angles are meafured by the Arch ofa great Circle, inter- cepted between the Sides containing the Angle, the Pole of that Circle being the Angular Point. 4.. Thofe are {aid to be great Circles, which bife& the Sphere. 5. Thofe Circles which cut each other at Right-Angles, pats through the Poles ofeach other, and the contrary. 6. Inevery Spherical Triangle, each Side js lefs thana Semi-Circle. 7. Inevery Spherical Triangle, any two Sides together are greater’ than the third, . ; 8. The Sum of the Sides of a Spherical Triangle is lef than two S mi-Circles, ‘ 9. If two Sides of a Spherical Triangle be equal to a Semi-Circle, the two Angles at the Bale (hall be equal to two Right-Angles 5 if they be lef thaa a Semi-Circle, the two Angles fliall be lefs; but