Add README.md to explain what is a transpose of matrix

math/transpose_of_matrix/README.md

@@ -0,0 +1,15 @@
+## Transpose of matrix
+
+In linear algebra, the transpose of a matrix is an operator which flips a matrix over its diagonal, that is it switches the row and column indices of the matrix by producing another matrix denoted as A<sup>T</sup> [1].
+
+It is achieved by any one of the following equivalent actions:
+- Reflect A over its main diagonal (which runs from top-left to bottom-right) to obtain A<sup>T</sup>.
+- Write the rows of A as the columns of A<sup>T</sup>.
+- Write the columns of A as the rows of A<sup>T</sup>.
+
+Formally, the <i>i</i>-th row, <i>j</i>-th column element of A<sup>T</sup> is the <i>j</i>-th row, <i>i</i>-th column element of A:
+
+![](https://upload.wikimedia.org/wikipedia/commons/e/e4/Matrix_transpose.gif)
+
+#### Reference
+[1] https://en.wikipedia.org/wiki/Transpose