In linear algebra, there are certain matrices which have the property that when they are multiplied with another matrix, the result is the identity matrix (the matrix with ones on its main diagonal and 0 everywhere). If is such a matrix, then is called invertible and its inverse is called , with:
There are algorithms for calculating the inverse of a matrix, with Gaussian elimination being a common example. The problem is that finding the inverse is relatively expensive to do for big matrices. Matrix inversion is used extensively in computer graphics.