Schaum's Outline of Theory and Problems of Beginning Calculus

Chapter 27Graphs and Derivatives of Sine andCosine Functions27.1 GRAPHSLet us first observe that cos x and sin x are continuous functions. This means that, for any fixedx = e,lim cos (0 + h) = cos 8 lim sin (0 + h) = sin 8h-0 h-0as is obvious from Fig. 27-1. Indeed, as h approaches 0, point C approaches point B. Therefore, thex-coordinate (the cosine) of C approaches the x-coordinate of B, and the y-coordinate (the sine) of Capproaches the y-coordinate of B.Table 27-1Now we can sketch the graphs of y = cos x and y = sin x. Table 27-1 contains the values of cos xand sin x for the standard values of x between 0 and n/2; these values are taken from Table 26-1. Alsolisted are the values for 2n/3 (120"), 3n/4 (135"), and 5n/6 (150"). These are obtained from the formulas202