75 } \right] \] It is easy to see that the rotation matrix corresponds to a 30° rotation. The matrix product is commonly written as \[ {\bf F} = {\bf R} \cdot {\bf U} \] where \({\bf R}\) is the rotation matrix, and \({\bf U}\) is the right stretch tensor that is responsible for all the problems in life: stress, strain, fatigue, cracks, fracture, etc. Note that the process is read from right to left, not left to right. \({\bf U}\) is applied first, then \({\bf R}\). This partitioning of the deformation.