This book is the outcome of many years of experience teaching courses that focus on how mathematics is used in economic analyses. We have found that, although most economics students know the basics of calculus and econom ic theory, they rarely encounter interesting ways to apply mathem atics to economics at the undergraduate level.In our teaching and in our book, we integrate m athematics and econom ics in a way that illustrates the insights that m athematics can bring to economic analysis.