First of all, an optical drive can be a CD, DVD, or BluRay drive. The button isn't invisible, it's just hidden in plain site by design. The previous pictures show its location, but here is one more. This is a picture of the top of a 660 showing 2 drives.
What is difference between an osteon and osteocyte? An osteon is the functional unit of cortical bone. Osteons contain osteocytes, which are cells that produce bone matrix.
Definition of Matrix. A matrix is a collection of numbers arranged into a fixed number of rows and columns. Usually the numbers are real numbers. In general, matrices can contain complex numbers but we won't see those here.Here is an example of a matrix with three rows and three columns: The top row is row 1.The leftmost column is column 1. This matrix is a 3x3 matrix because it has three rows and three columns. In describing matrices, the format is: rows X columns. Each number that makes up a matrix is called an element of the matrix. The elements in a matrix have specific locations.he top row is row 1. The leftmost column is column 1. This matrix is a 3x3 matrix because it has three rows and three columns. In describing matrices, the format is: rows X columns. Each number that makes up a matrix is called an element of the matrix. The elements in a matrix have specific locations.