ACUTE TRIANGULATIONSDoctoral ThesisbyLiping YuanSupervised byProf. Dr. Tudor ZamflrescuDEPARTMENT OF MATHEMATICSDORTMUND UNIVERSITYApril 2006.CONTENTSAcknowledgements 5Chapter 1. Introduction 7Chapter 2. Acute Triangulations of Convex Quadrilaterals 11x2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11x2.2 Preliminaries . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11x2.3 Acute Triangulations of Trapezoids . . . . . . . . . . . . . . . . 12Chapter 3. Acute Triangulations of Pentagons 17x3.1 Preliminaries . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17x3.2 Acute Triangulations of Pentagons . . . . . . . . . . . . . . . . 19Chapter 4. Acute Triangulations of Polygons 27x4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27x4.2 Preliminaries . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28x4.3 Acute Triangulations of Polygons . . . . . . . . . . . . . . . . . 29x4.4 Non-obtuse Triangulations of Polygons . . . . . . . . . . . . . . 36Chapter 5. Acute Triangulations of Surfaces 43x5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43x5.2 Acute Triangulations of Double Convex Quadrilaterals . . . . . 453x5.3 Acute Triangulations of Double Convex Pentagons . . . . . . . 47x5.4 Double Symmetric Smooth Convex set . . . . . . . . . . . . . . 53x5.5 Acute Triangulations of Flat Tori . . . . . . . . . . . . . . . . . 55x5.6 Acute T of Flat M˜obius Strips . .