Wentworth, G. A. (George Albert), 1835-1906 · Boston, Ginn & company · leaf 39
90° + x, and they must lie in adjoining quadrants. Therelations between their functions were found in Sect. XXV,p. 48, but only for the case when x is acute. These relations,however, may be shown to hold true for all values of x. In a unit circle (Fig. 47) drawtwo diameters PR and QS per-pendicular… … BFig. 47 OSN. Therefore, OM= QH= OK = NS, d PM = OH= RK = ON. Hence, taking into account the algebraic sign,sin A OQ= cos A OP; sin A OS = cos A OR;cos AOQ = —sin A OP; cos AOS == — sin AOR ;sin A OR = cos A OQ; sin (360° + A OP) = cos A OS;cos AOR= - sin A OQ; cos (360° + AOP) = - sin A OS. In all…
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