THE Ʋses of this Line are principally two. The one is, To protract or lay down upon Paper an Angle of any quantity (that is, of any number of degrees) required.— The other Ʋse is, If an Angle be already protracted or laid down, to finde how many degrees and parts of a degree it containeth. —In both which I would have the Reader very perfect, because very much contained in this Book hath dependence thereupon.
And here it will be necessary that I give you the Definiti∣on of an Angle. Know therefore that an Angle is the Inclination or bowing of two right Lines the one to the o∣ther.—As the two right Lines C A and B A incline the one to the other, and touch or meet each other in the Point A, in which Point, by rea∣son of the inclination of the said Lines, is made the Angle C A B.