Figure 4-12. Trigonometric function of any angle
g. A supplementary angle is an angle that when added to another angle equals 180. Since all
angles in the second quadrant are larger than 90, their supplements must be acute angles. Assuming
that angle XAB in Figure 4-13, page 20, can have any value from 90€ to 180€, you can derive the
following formulas for the functions of any angle in the second quadrant.