This book is only available from us in German, but you can find an English translation here: https://www.waldorfpublications.org/collections/waldorf-publications/products/topics-in-mathematics-grade-11
Topics in Mathematics for the 11th Grade
The series Mathematics for the High School was specifically designed with math teachers in mind. Not only are the books a useful resource for gaining familiarity with teaching approaches used in a Waldorf school, but they are also a source of inspiration - offering fresh perspectives and new insights - for courses that have perhaps been taught many times.