My math professor recently told us that she wanted us to be able to answer
Note the pattern:
This is something of a mathematical coincidence as far as I know, so don't try to extend this to other angles; and it goes backwards for
. Once you have these, you can find the other angles you want by drawing them on the unit circle and figuring out whether the values should be positive or negative, whether they should be or , or otherwise whether they are "small" (), "medium" () or "large" ().