The description and use of the universall quadrat.: By which is performed, with great expedition, the whole doctrine of triangles, both plain and sphericall, two severall wayes with ease and exactness. Also the resolution of such propositions as are most usefull in astronomie, navigation, and dialling. By which is also performed the proportioning of lines and superficies: the measuring of all manner of land, board, glasse; timber, stone. &c.
Stirrup, Thomas.
CHAP. XXIX. To finde an angle, by knowing the other oblique angle, and the side opposite to the angle given.
- As the cosine of the side,
- To the cosine of the angle given:
- So is the radius,
- To the Sine of the angle required.
So in the rectangle ABC, having the angle BAC 37 degrees 30 minutes, and the side BC 33 degrees 36 minutes, to finde the angle ACB: place the threed at the intersection of the contrary Sine of 56 degrees 24 minutes, (the complement of BC) with the right sine of 52 degrees 30 minutes (the complement of the angle BAC) and it will cut the contrary sine of 90 degrees, at the right sine of 72 degrees 16 minutes, the angle ACB, which was required.
