The resolution of the acceleration vector of rigid body moving along a space curve is well known thanks to Siacci [1]. In this resolution, the acceleration vector is stated as the sum of two special oblique components in the osculating plane of the point of the curve. In this paper, we have studied the Siacci’s theorem for the curves on regular surfaces in 3-dimensional Euclidean space. Also, an example is given for a helix lying on a cylinder.

In this paper, we introduce the concept of consimilarity of split quaternions and split quaternion matrices. In his regard, we examine the solvability conditions and general solutions of the equations and in split quaternions and split quaternion matrices, respectively. Moreover, coneigenvalue and coneigenvector are defined for split quaternion matrices. Some consequences are also presented.