Secrets of Triangles: A Mathematical Journey

by Alfred S. Posamentier, Ingmar Lehmann

Everyone knows what a triangle is, yet very few people appreciate that the common three-sided figure holds many intriguing "secrets." For example, if a circle is inscribed in any random triangle and then three lines are drawn from the three points of tangency to the opposite vertices of the triangle, these lines will always meet at a common point - no matter what the shape of the triangle. This and many more interesting geometrical properties are revealed in this entertaining and illuminating book about geometry. Flying in the face of the common impression that mathematics is usually dry and intimidating, this book proves that this sometimes-daunting, abstract discipline can be both fun and intellectually stimulating. The authors, two veteran math educators, explore the multitude of surprising relationships connected with triangles and show some clever approaches to constructing triangles using a straightedge and a compass. Readers will learn how they can improve their problem-solving skills by performing these triangle constructions. The lines, points, and circles related to triangles harbor countless surprising relationships that are presented here in a very engaging fashion.Requiring no more than a knowledge of high school mathematics and written in clear and accessible language, this book will give all readers a new insight into some of the most enjoyable and fascinating aspects of geometry.

Genres: Mathematics, Science, Nonfiction

392 pages, Hardcover

First published January 1, 2012

About the author

Alfred S. Posamentier (born October 18, 1942) is among the most prominent American educators in the country and is a lead commentator on American math and science education, regularly contributing to The New York Times and other news publications. He has created original math and science curricula, emphasized the need for increased math and science funding, promulgated criteria by which to select math and science educators, advocated the importance of involving parents in K-12 math and science education, and provided myriad curricular solutions for teaching critical thinking in math.

Dr. Posamentier was a member of the New York State Education Commissioner’s Blue Ribbon Panel on the Math-A Regents Exams. He served on the Commissioner’s Mathematics Standards Committee, which redefined the Standards for New York State. And he currently serves on the New York City schools’ Chancellor’s Math Advisory Panel.

Posamentier earned a Ph.D. in mathematics education from Fordham University (1973), a Master’s degree in mathematics education from the City College of the City University of New York (1966) and an A.B. degree in mathematics from Hunter College of the City University of New York.

Posamentier was born in Manhattan in New York City, the son of Austrian immigrants. He has one daughter (Lisa, born in 1970), and one son (David, born in 1978). He resides in River Vale, New Jersey and is the current Dean of the School of Education and professor of mathematics education at Mercy College, New York. He was formerly professor of mathematics education and dean of the School of Education at The City College of the City University of New York, where he spent the previous 40 years.

Reviews

[John · Rating 4 out of 5]

If you think you know everything about simple plane triangles read this book. Significant theorems about humble triangles are still being discovered. There are more real plane triangles than natural numbers and after millennia of study I suspect we are just getting started.

[Gregory Tabachnik · Rating 5 out of 5]

Very well written book on properties of triangles. In fact, the book is not just about triangles, but about various fascinating aspects in plane geometry.