Wentworth, G. A. (George Albert), 1835-1906 · Boston, Ginn & company · leaf 24
§8. Functions of 30° and 60°. Let ABC be an equilateral triangle in which the lengthof each side is equal to 1; and let CD bisect the angle C.Then CD is perpendicular to AB and bisects AB; hence,AD = I and CD = VT~T= Vf = lV5. In the right triangle J.DC, the angle ACD = S0°, and theangle CAD = 60°.… … V3esc 30° — sec G0° = 2. The results for sine and cosine of 30°, 45°, and 60° may beeasily remembered by arranging them in the following form: Angle. . . 30° 45° 60° £ = 0.5 Sine .... h *V2 *V3 *V2 = 0.70711 Cosine. . . iV3 *V2 I £V3 = 0.86603 / > OSAPTM II. THE RIGHT TRIANGLE. § 9. The Given…
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