books.google.com - Problem solving in mathematics is often thought of as a one way process. For example: take two numbers and multiply them together. However for each problem there is also an inverse problem which runs in the opposite direction: now take a number and find a pair of factors. Such problems are considerably...http://books.google.com/books/about/Inverse_Problems.html?id=RjKNnqK_Ef4C&q=Tartaglia&utm_source=gb-gplus-shareInverse Problems