This book is a handbook on topics in Plane Trigonometry for students in Middle / High School. We have covered the topics like - Measurement of Angles, Basic Trigonometric Ratios, Trigonometric Ratios across the 4 quadrants, Trigonometric functions of angles of any size and sign, General Expressions for all Trigonometric Ratios, Trig. Ratios of Sum and difference of two angles, Multiple and Sub-multiple angles, Solutions of triangles, Heights and Distances and Inverse Circular Functions. Each chapter is follows a simple structure. A definition of terms and detailed explanation of concepts; followed by derivation of useful formulas through first principles. A few problems are solved in order to give a flavor of the problem solving process. This book is intended to help the student to understand ways to build an airtight reasoning on how the problem solving process moves towards the final answer. This serves as a demonstration of our understanding of the subject - basics, formulas and methods of manipulation.