All angles are on the unit circle, but only the special ones have exact values, and all the others, such as your example, can only be had as a decimal approximation found by calculator. To get the decimal approximation for your example, on your TI-83 or TI-84 calculator, press these keys: 2ND SIN 1 / 3 ) ENTER Get 0.3398369095 if your calculator is in radian mode, or 19.47122063° if your calculator is in degree mode. Edwin