Rare Books

A breefe treatise of sphaericall triangles, : wherein is handled the sixteene cases of a right angled triangle, being all extracted out of one diagram, and reduced into theorems, with the totall sine in the first place, so that by addition onely, they may be effected. As also, the twelue cases of an oblique sphaericall triangle, being likewise reduced into theorems, whereby with one or two additions at the most, any of them may be resolued by helpe of this canon following made with secants, and that only by such numbers as are therein to be founde, without first making any substraction, or vsing any mentall operation. Most commodious and necessarie