I'm basically homeschooled in math so please forgive me if this question seems simple, but I have never been able to find a book that shows how radians are calculated. Through inspection I've sorta determined 45 degrees = pie/4, 60 degrees = pie/3, 90 degrees = pie/2, 180 = pie and so forth but I input pie into my calculator and change to degrees and it returns 200? Is there a formula I can use to calculate radians? There is no way I can commit the tables to memory... I can understand why before calculators, radians were easier to use, is there and reason why we continue to use radians over decimal today? Maybe if I understood them their continued use would make more sense to me. Many thanks!