You can make choices in the View menu that affect the appearance of matrices on the screen. Helper Lines and Input Boxes can be shown or hidden. The default is to show them to make it easier to handle entries on the screen. However, matrix helper lines and input boxes may not appear when you preview or print the document. For this reason, you will generally want to put brackets around matrices. Scientific Notebook generally presents the result of an operation on matrices with the same brackets as the original matrices. The choice of round or square brackets does not affect the mathematical properties of the matrix. Vertical straight brackets are interpreted as a mathematical operation (called a determinant) so they should be avoided for general use.
To enclose a matrix in brackets