Some students just don't take the time to memorize the outputs of the trigonometric operations on the more common angles. If you can memorize the values of the trig functions on the angles 0, 30, 45, 60 and 90 degrees (0, pi/6, pi/4, pi/3 pi/2 radians), you will save a ton of time on trigonometry, precalculus, calculus and physics assignments/tests.
Here's a demonstration of a pattern in the values of the sin and cos of these angles that might help you remember these values more easily.
angle | 0 | 30 | 45 | 60 | 90 |
sin | rt(0)/2 | rt(1)/2 | rt(2)/2...