- Here's how you remember the exact values of sines and cosines. First, notice the square root of 0 is 0 over 2, which is 0. Square root of 1 is just 1 over 2. Square root of 4 over 2 is 2 over 2, which is 1. 

And then you make a table with all the special angles from 0 through 90 degrees. Put square root over 2 for every blank, and now you start filling in the blanks by 0, 1, 2, 3, 4, and you go backwards for cosine. 4, 3, 2, 1, 0. And then you replace square root of 0 over 2 by 0, this one by 1/2, this one by 1, and do the same thing for the next row. There.