Posamentier A. Math Motivators. Investigations in Geometry 1982

Textbook in PDF format

This book is a set of versatile enrichment exercises that covers a wide variety of topics in geometry-Euclidean, post-Euclidean, and non-Euclidean. Several criteria have been used in developing the investigations and in selecting the topics that have been included. All of them bear heavily on your concerns for curriculum goals and classroom management.
Most of the investigations in this volume can be used to enhance, extend, and reinforce the concepts and skills that already make up the better part of your curriculum and course goals