University of Minnesota math Prof. Donald Kahn, husband of longtime state Rep. Phyllis Kahn, died unexpectedly Friday night.

The couple had been married for 58 years. Donald Kahn, 79, had recently completed a book on photography, friends said.

Kahn met Phyllis when they were students at Cornell University, and he received a Ph.D in mathematics from Yale University in 1961.

He taught math at Columbia University before moving to Minneapolis to teach at the U.

He was a lifelong photographer, in addition to being a cellist and a supporter of the musicians during the Minnesota Orchestra lockout.

“He was a good political strategist — he always helped Phyllis on all of her campaigns,” said attorney Brian Rice, a family friend who’s worked on Phyllis Kahn’s campaigns. “He was so supportive of everything she did.”

Phyllis Kahn, DFL-Minneapolis, has served more than 40 years in the House and won re-election this fall.

Her territory, District 60B, is one of the most racially and economically diverse in Minnesota and includes the U, Cedar-Riverside, East River Road, Nicollet Island East and Seward neighborhoods.

The couple have two grown children. Private services are planned.