Printed for F. WINGRAVE, Succeffor to Mr. NOURSE, in the Strand;

By LUKE HANSARD, N° 6, Great Turnstile, Lincoln's Inn Fields.

1799.

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Plane Trigonometry.

DEFINITION S.

"PLA

LANE Trigonometry is the art whereby, having given any three parts of a plane triangle, (except the three angles) the reft are determined. In order to which, it is not only requifite that the peripheries of circles, but alfo certain right-lines in, and about, the circle, be fuppofed divided into fome affigned number of equal parts.

2. The periphery of every circle is fuppofed to be divided into 360 equal parts, called degrees; and each degree into 60 equal parts, called minutes; and each minute into 60 equal parts, called feconds, or fecond minutes, &c.