Hi, I've been experimenting with the quaternionspackage. (The free download, not the commercial package). There seems to be an error in the calculation of the inverse: with (Quaternions); [*, +, -, Qabs, Qadd, Qamplitude, Qangle, Qarccos, Qarccosh, Qarccot, Qarccoth, Qarccsc, Qarccsch, Qarcsec, Qarcsech, Qarcsin, Qarcsinh, Qarctan, Qarctanh, Qargument, Qaxial, Qceil, Qcolatitude, Qconjugate, QconvertToFrac, Qcos, Qcosh, Qcot, Qcoth, Qcsc, Qcsch, Qdefine, QdivLeft, QdivRight, Qdot, Qeval, Qexp, Qfloor, Qfrac, Qicoeff, Qinverse, QisCommutable, QisEqual, QisPure, QisScalar, Qjcoeff, Qkcoeff, Qlength, Qln, Qlongitude, Qmagnitude,