CIRCULAR FUNCTIONS Consider the rectangular coordinate system shown in Figure 6.1. The coordinate is positive to the right of the origin and the coordinate is positive above the origin. The radius vector r shown terminating on the point is shown rotated by the angle up from the axis. The radius vector r has component values and .
Temme, N.M, & Zayed, A.I. (2002). Special functions. In CRC Standard Mathematical Tables and Formulae, 31st Edition (pp. 499–614).