He influenced one of the most famous calculus teachers in America, Jaime Escalante, the former Garfield High School instructor whose success with inner-city students in Los Angeles was told in the 1988 movie "Stand and Deliver."
Escalante, who met Leithold in the 1980s, consulted with him about when to teach certain concepts, such as limits and differentiation. He invited Leithold to lecture to his classes at Garfield and used copies of Leithold's textbook that Leithold helped him obtain at a discount.
"I called him my advisor," Escalante told The Times on Saturday from his son's home near Sacramento. "He was one of the great mathematicians. His book had beautiful problems. It made us believe that anybody could do calculus."
Leithold, who lived alone, failed to show up for class two Fridays ago. His body was discovered by a parent who accompanied three worried students to his house after school that day.
A spokesman for the coroner's office said Leithold had heart and pulmonary disease and attributed the death to natural causes.
His students were distraught at the loss of their teacher -- and not merely because the Advanced Placement exam was just days away.
"With any other teacher who tried to give us as much work, there would have been a class rebellion," said senior Matthew Mesher, 17. "But he inspired you to do mathematics. His face would just light up."
Leithold spent most of his 50-year career in college classrooms. In addition to Cal State L.A., he taught at Phoenix College in Arizona, the Open University of Great Britain, USC and, most recently, Pepperdine University, where he was an adjunct professor of mathematics.
As a boy growing up in San Francisco, he was academically gifted. He attended Lowell High School, an elite public school that accepted only the brightest students in the city. He later worked his way through UC Berkeley, where he earned his bachelor's, master's and doctorate degrees.
He was teaching in Arizona when a publisher approached him about writing a textbook. "The Calculus with Analytic Geometry" was published in 1968 by Harper and Row and quickly became a bestseller in English and several other languages, including German, Spanish and Chinese. In its latest edition, it is called simply "The Calculus 7."
