This book provides an introduction to several mathematical topics of importance in Computer Science but often considered to be outside the scope of traditional Discrete Methods courses. It offers basic treatments of Calculus, Complex Numbers, Statistics, and Linear Algebra with a particular emphasis on Spectral Methods. The presentation is intended for students with minimal mathematical background. Its principal aim being to emphasize the significant applications in modern CS for which some awareness of these fields is essential, e.g. Machine Learning, Data Science, Computational Game Theory, and Optimization. The focus is, therefore, directed towards applications in CS rather than detailed mathematical exposition. About the author: Paul Dunne is a Professor of CS at the University of Liverpool where he has worked since 1985. He studied CS at the University of Edinburgh (1977-1981) and completed his PhD research at Warwick University (1981-1984). In his time at Liverpool he has had experience in teaching all levels of undergraduate from first year through to Honours year presenting courses on Computability and Complexity Theory, Algorithms, Operating Systems, and the topic of the present book. He has published research in a range of fields from Boolean Function complexity, phase transition phenomena, AI and Law, complexity in multiagent systems, and has recently been most active in the area of models of Computational Argument.