The English globe being a stabil and immobil one, performing what the ordinary globes do, and much more / invented and described by the Right Honorable, the Earl of Castlemaine ; and now publish't by Joseph Moxon ...

Of the Use of the LINE of SINES, markt with S.

[illustration]

I. How to find the Sine of any Angle, according to any Radius.

SUppose the Sine of the Angle you require be 50, take the Radius between your Compasses, and put it over at the extremity of the Sector, that is to say, at 90 and 90, and the Parallel at 50 and 50 will be the Sine of 50 Degrees, accord∣ing to that Radius.

II. How to find the Chord of any Arch.

SUppose you would have the Chord of an Arch of 50 Degrees, open your Compasses at the length of the given Radius, and put it over at 90 and 90, then take with your said Com∣passes the Parallel, at the Figures 25 and 25 on the Sector, (i. e.

at the Figures of half the Degrees given) and prick or measure it twice upon any streight Line, and that will be the required Chord.

III. How to make an Angle of any value, as also how to find the value of any Angle already drawn.

[illustration]

SUppose you are to make an Angle of 50 Degrees, draw a Line, as (for Example sake) AD, and taking any Point in it, as B, open your Compasses to a convenient Radius, and put one Foot on B, and describe the blind Arch CF, then taking between your Compasses the Chord of 50, according to the Radius of the said Arch, put one Foot on C, and the other marking at suppose E, draw the Line BE, and you have the required Angle, to wit, the Angle EBC. But if the Angle you would make be above 90 Degrees, as suppose 130, make the Angle of its Supplement, viz. the Angle of 50 as before, and the Angle on the other side, viz. EBA will be the Angle you look for:

Here therefore you see how to find the value of any Angle already drawn, as suppose the Angle EBC, since 'tis but de∣scribing a blind Arch, as CF, and setting over (on the Sector) the Radius of the said Arch at 90 and 90; for if you observe where the measure of this Arch (viz. C. E) marks a Parallel on the Sector, as before, the Figures there (to wit, 25) being doubled (and amounting consequently to 50) will be the requir'd An∣gle.

As for the Tangent and Secant of any number of Degrees, the Noble Author has himself showd you how to find them at pag. 71. and so gentle Reader having finish'd my promise, I bid you Farewel.