February 14, 1892 - August 10, 1992

Teresa Cohen was born in Baltimore, Maryland, on Valentine's Day 1892. She attended the Friends School in Baltimore where she credits one of her teachers with sparking her interest in mathematics and teaching. In an interview given at the age of 94, she said:

"He tried to make you see that you wanted to reason. You didn't want to remember, you wanted to reason things. And I became so fascinated with algebra that I started working out on my own."

Cohen earned her bachelor of arts degree in mathematics and physics at Goucher College in 1912, with a minor in chemistry. Her graduate work was done at Johns Hopkins University where she earned her master's degree in 1915 and her Ph.D. in mathematics in 1918, only 7 years after Clara Bacon became the first woman to receive a Ph.D. in mathematics at Johns Hopkins. Cohen's Ph.D. dissertation, written under the supervision of Frank Morley, was on "Investigations of the Plane Quartic." She published four papers on this subject:

- "The Asymptotic Equation and Satellite Conic of the Plane Quartic," American Journal of Mathematics, Vol. 38, No. 3 (July 1916), pp. 325-336 [JSTOR]
- "A Comitant Curve of the Plane Quartic," American Journal of Mathematics, Vol. 39, No. 3 (July 1917), pp. 221-232 [JSTOR]
- "The Cayleyan Curve of the Quartic," Proceedings of the National Academy of Sciences of the United States of America, Vol. 3, No. 7 (July 1917), pp. 447-450 [JSTOR]
- "Investigations on the Plane Quartic," American Journal of Mathematics, Vol. 41, No. 3 (July 1919), pp. 191-211 [JSTOR]

Upon completing her doctoral degree, Cohen taught in the Johns Hopkins summer school from 1918 to 1920. In September of 1920 she received a telegraphed job offer from Joseph Willard, head of the mathematics department at Pennsylvania State University and a colleague of Cohen's uncle who was on the Johns Hopkins mathematics faculty. Willard had a sudden need for an additional mathematics instructor for a class scheduled at the last minute. Two days later Cohen arrived in State College to begin a teaching career that lasted over 60 years. She was the first female member of the university's mathematics department, and the only woman for her first three-and-a half years at the school. According to Raymond Ayoub, one of Cohen's former colleagues at Penn State,

"It was quite unusual for a woman to function in what was then regarded as a masculine domain. She was a pioneer who helped pave the way for other women to go and do likewise. Although she had the natural gifts to pursue a career in mathematical research, she chose what she considered to be the better part—that of devoting all of her energies to teaching and helping students."

Cohen was promoted to assistant professor in 1921, to associate professor in 1939, and to full professor in 1945 (one of only a few university full professors in the country at that time who were female.) Each summer she would return to her home in Baltimore to play the violin and indulge in chamber music. Due to university regulations, she officially retired from Penn State at the end of 1961 but spent much of the next twenty-four years tutoring math students for free. Her usual routine was to walk the five blocks to campus each morning and be available to help any student between 9:30 a.m. and 4:30 p.m., or to fill in for an ailing colleague. Faculty members, other students, and relatives of former students would all refer those needing additional help in mathematics to her campus office. As she once said, "I just like the pleasure of explaining and seeing someone understand." She continued devoting her time and energy to students until an accident at the age of 94 forced her to enter a nursing home in Baltimore.

While in her 80's Cohen co-authored a paper with William Knight, at that time an assistant professor at Penn State, about the convergence and divergence of the p-series ∑_{(n=1..∞) }n^{–p}. In their article they presented a simple proof of the convergence for p > 1 that relied on separating the partial sums into odd and even-numbered terms, an argument that could be presented to high school students who might not be familiar with the more traditional integral test. The paper was published in Mathematics Magazine in May, 1979.

In 1982 the Department of Mathematics at Penn State established the Teresa Cohen Service Award for excellence in undergraduate teaching to honor her achievements. The award is given every two years to two faculty members, one at the main University Park campus and another at one of the nineteen Commonwealth campuses. In 1987 the department established the Teresa Cohen Tutorial Endowment Fund to foster an undergraduate tutoring program, which in 1991 became known as the Sperling-Cohen Program. As described by Jerry Bona, head of the department at that time,

"The tutoring program is our way of providing future Penn Staters with the sort of personal attention and caring Dr. Cohen provided for their predecessors. One of her greatest gifts to us was that she showed us what to do and how to do it. We are merely following her example."

Teresa Cohen died in Baltimore in 1992 at the age of 100. She had been a member of the American Mathematical Society, the Mathematical Association of America, Pi Mu Epsilon, and Sigma Delta Epsilon, the national honor society for women in science. She was a charter member of the Penn State chapter of Phi Beta Kappa.

- ABVF/Cohen, Teresa – Penn State University Archives, The Pennsylvania State University Libraries
- Mathematics Genealogy Project
- Author Profile at zbMath

Photo credit: PorVF/Cohen, Teresa – Penn State University Archives, The Pennsylvania State University Libraries. Used with permission.