This introduction to basic analysis presents a careful development of the real number system and the theory of calculus on the real line, extending the theory to real and complex planes. Designed as a first encounter with rigorous, formal mathematics for students with one year of calculus, the work features extended discussions of key ideas and detailed proofs of difficult theorems. Authors David F. Belding and Kevin J. Mitchell are Professors of Math at Hobart and William Smith Colleges in Geneva, New York. Their approach emphasizes the connections between ideas, rather than rote, computational aspects of calculus. Their two-part treatment begins with the real number system and covers functions, limits, and continuity, as well as differentiation and integration and aspects of sequences and series. The second part explores calculus in two dimensions in addition to line integrals and Green's theorem. The text concludes with a concise survey of complex analysis.