A treatise on special or elementary geometry (1877)
Olney, Edward, 1827-1887, Olney, Edward, 1827-1887. Elements of trigonometry, plane and spherical · New York : Sheldon · leaf 359
eca:^ sma; (7) sec a: = 1 + tan x; (8) coseca; = 1 4- cota; (9) vers a; = 1 — cos a;;(10) covers a; = 1 — sin a;. (The forms sina, seca;, etc., signify tlie square of the sine, thesquare of the secant of x, etc., and are read sine square a;, secantsquare x etc. The student should distinguish… … Fig. 4. (1). In the right-angled triangle POD,pd + OD = 0P> or sm^a; + cosa; = 1,since OP = radius = 1. (2). From the similar triangles POD and TOA, AT PD sin a; £J- = ~^, or tan x = OA OD cos a-. (3). From the similar triangles POcf andiOa, at Pd cos a; = ^^.. or cot X — —.— . sma; ^ = 7^ 01…
Geometry · Trigonometry
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