cos(arcsin(-1/3)) how to do it by hand?? 1. The problem statement, all variables and given/known data Solve without a calculator cos(arcsin(-1/3)) 3. The attempt at a solution now i have fount the solution to be (-2/3)(2^(1/2)) now not only did my calculator come up with that but between the SSS formula and pythagorean formula( i think is what we cal it, a^2+b^2....) i was able to get the same answer but the question says not to use a calculator and using those formulas of course im going to have to use a calculator to figure out some of the roots and what not. I havent had to do this stuff for quite sometime now im a ways past precalc but i was trying to help a friend and im not sure how to do this without a calculator or a root table and any other aids other than my mind. So being that this is precalc i would assume there is a easy way do do this beyond what im trying if the teacher expects it to be done without a calc so if you know how please enlighten me.