Wentworth, G. A. (George Albert), 1835-1906 · Boston, Ginn & company · leaf 24
cos2Ainto a form containing only cos A. 29. Prove that sin A -f cos A = (1 + tan A) cos A. 30. Prove that tan A -f cot .4 = sec A X esc .4. TRIGONOMETRIC FUNCTIONS. 15 1 § 7. Functions of 45°. Let ABC (Fig. 6) be an isosceles right triangle, in whichthe length of the hypotenuse ABis equal to 1;… … §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°.…
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