Worked it out, thanks for the help!
Oi Arch, that way I showed you was kind a of a brute force method that'll always work if you can't see what to do. It works but it's a slog. A much neater way would be to evaluate sin(3@ - @). See if you can figure it out, it only takes a line or so. The thing is you need to use these things all the time to spot tricks like that.
