David Wilson Henderson, professor emeritus of mathematics, died Dec. 20 in Newark, Delaware, from injuries suffered when he was struck by a vehicle in a pedestrian crosswalk in Bethany Beach, Delaware. He was 79.

According to published reports, Henderson was struck shortly after 5 p.m. on Dec. 19. After being taken to nearby Beebe Medical Center in Lewes, Delaware, Henderson was transported to Christiana Hospital in Newark, where he died the next day.

Henderson was born Feb. 23, 1939, in Walla Walla, Washington, but completed high school in Ames, Iowa. He received his bachelor’s in math, physics and philosophy from Swarthmore College in 1961, and earned his Ph.D. in geometric topology in 1964 from the University of Wisconsin, Madison.

He spent two years as a postdoctoral researcher at the Institute for Advanced Study in Princeton, New Jersey, before joining Cornell, where he taught for 46 years until his retirement in 2012.

Henderson was passionate about mathematics education. He joined the Graduate Field of Education in 1970 and supervised the research of more than 40 students over the years.

His mathematical research focused on geometric aspects of topology. From 1963-95, he produced 37 published papers on the topic, and was chair for eight Ph.D. theses related to geometric topology from 1970-88.

Henderson’s first Ph.D. advisee, Ross Geoghegan, Ph.D. ’70, said a topology class for first-year graduate students – led by Henderson using the Moore method, in which students themselves, with no textbook, guide the instruction – was pivotal in his academic career.

“No Moore-style course had ever been taught at Cornell,” said Geoghegan, a research professor of mathematics at Binghamton University. “I was one of 30 students [in the class], and the course, particularly the method of instruction, made a huge impact on me.”

Henderson’s commitment to mathematics education never waned. In 2005, he accepted an invitation to join the core curriculum development team of the Algebra Project, a National Science Foundation-supported initiative that helps ensure that all students learn the mathematics they need to enter college and not need remedial courses.

In 2011, he joined a project aimed at developing coherent curricula for K-5 math and science, writing geometry curriculum. And in 2016, Henderson was part of a research project called “Function Learning Progressions,” funded by a four-year National Science Foundation Discovery Research K-12 grant to both the Algebra Project and the nonprofit Educational Testing Service.

“David was a vigorous advocate of helping students make sense of math through active learning and exploring for themselves, as opposed to sitting passively in a lecture,” said Steven Strogatz, the Jacob Gould Schurman Professor of Applied Mathematics. “He was a caring and dedicated teacher for all students, not just math majors.”

Henderson had a direct impact on math education close to home, too. Steven Weissburg, chair of the math department at Ithaca High School, said Henderson conducted summer workshops for secondary-school teachers in the 1990s, with experiential learning at the core.

“That’s really what made the workshops so great,” Weissburg said. “He really encouraged us to hypothesize, conjecture, explore, revise. David’s workshops helped many of us to improve our teaching methods and provided a great opportunity to think and network. … He was an outstanding mathematician, but also a great educator and an inspiring person to work with.”

Among his academic honors, Henderson was a member of the American Mathematical Society, the Mathematical Association of America, the National Council of Teachers of Mathematics, Phi Beta Kappa, and scientific research honor society Sigma Xi.

Henderson is the author of “Experiencing Geometry on Plane and Sphere” (1996) and revised editions of the book in 2001 and 2005 with wife Daina Taimina, a retired adjunct associate professor of math at Cornell. According to Taimina, they had plans to begin work on a fourth edition; Henderson also wrote “Differential Geometry – A Geometric Introduction” (1998), with writing input from Taimina.

In addition to Taimina, Henderson is survived by four children and four grandchildren, as well as two brothers and a sister.

A memorial service is scheduled for Feb. 23 at 11 a.m. in Anabel Taylor Hall.

This story also appeared in the Cornell Chronicle.