DEAR SUBSCRIBERS: I got a domain error on the following equation. I was wondering whether or not someone would be able to help me with it. (E2+F2)-(2*E*F*cos(A)) -> D (B2-D2-F2)/(-2*D*F) -> U cos-1(U) -> B I was planning on using this as part of a program used to calculate angles and sides using the law of cosines. Thank you sincerelly ~BHegge7615