hether those new statements make sense, what their connection to reality is. This results in a collection of statements, a story, that is no longer easily understood. So, people stop trying to understand and focus on results only. If results are all right, this validates the mathematical procedure. This instrumentalist point of view [Pop34] reduces mathematics to a toolbox. As a consequence, mathematics often is more likely to conceal than to clarify the nature of things. It is no longer telling us a story and hence looses its attractiveness towards many -young- people. People are fascinated by stories, and telling stories is what languages are all about4. In this text, we've tried to keep the story we tell in mathematics consistent with the one we tell in English. It is attempted to clarify mathematical derivations as much as possible through intuitive (geometrical) interpretations. These interpretations are sum- marized in a section called "The story behind the math" that comes at the beginning of most chapters. In this way, we aim for mathematical accuracy while avoiding that the basic message gets lost in a jungle of equations. 1.3 Outline of this book This book is subdivided into six chapters. Each chapter starts with a brief summary followed by an introduction that reviews existing state of the art methods to solve sim- ilar problems. Chapters 3 to 5 contain the technical core. When relevant, it contains a section "The story behind the math" that attempts to provide a clear and intuitive 3 Of course, this perception strongly depends upon the engineering discipline being considered. Me- chanical engineering, for example, has a long-standing tradition which dates back to way before the advent of computers. Lack of computers forced people to develop, for example, sophisticated mathematical ap- proximation strategies. On the other hand, development of micro-electronics went in parallel with that of computing devices. As a consequence, circuit design practice heavily relies on virtual prototyping using computer-