I'll be up front and tell you guys that this is part of an assignment, but I'm only asking about this one thing that has been giving me fits for the past hour. Basically, in the context of a larger problem, I need to calculate an angle; specifically by taking the arcsine of 2/3: Code: theta = asin (2/3); That is what I am attempting to use, but it is evidently incorrect in some way because the output claims theta is 0.000000 (theta is of type double). FWIW, I have initialized the variable theta to 0 on the suggestion of my instructor.  I checked the syntax and it seems right, but surely I am missing something. Let me know if you want the entire program. Thanks for helping a novice programmer who is feeling like a noob!