Wentworth, G. A. (George Albert), 1835-1906 · Boston, Ginn & company · leaf 36
unit circle (Fig. 45) draw two diameters PR and QSequally inclined to the horizontal diameter A A, or go thatthe angles A OP, AOQ, AOR, andAOS shall be equal. From thepoints P, Q, R, S let fall perpen-diculars to A Ai the four righttriangles thus formed, with acommon vertex at O, are equal;because… … 48 PLANE TRIGONOMETRY Therefore, %n absolute value, sin A OP = sin A OQ = sin ^ 0# sin .4 05. And from Sect. XXIV, p. 44, it follows that in absolutevalue the cosines of these angles are also equal j and likewise the tangents, the cotangents, thesecants, and the cosecants.* Hence, For every acute…
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