Forsyth was born in
Glasgow on 18 June 1858, the son of John Forsyth, a marine engineer, and his wife Christina Glen. Forsyth studied at
Liverpool College and was tutored by
Richard Pendlebury before entering
Trinity College, Cambridge, graduating
senior wrangler in 1881. He was elected a fellow of Trinity and then appointed to the chair of mathematics at the
University of Liverpool at the age of 24. He returned to Cambridge as a lecturer in 1884 and became
Sadleirian Professor of Pure Mathematics in 1895. He was elected President of the
Mathematical Association for 1903. Forsyth was forced to resign his chair in 1910 as a result of a scandal caused by his affair with Marion Amelia Boys,
née Pollock, the wife of physicist
C. V. Boys. Boys was granted a divorce on the grounds of Marion's adultery with Forsyth. Marion and Andrew Forsyth were later married. Forsyth became professor at the
Imperial College of Science in 1913 and retired in 1923, remaining mathematically active into his seventies. He was elected a
Fellow of the Royal Society in 1886 He was a Plenary Speaker of the
ICM in 1908 at Rome. He is now remembered much more as an author of treatises than as an original researcher. His books have, however, often been criticized (for example by
J. E. Littlewood, in his ''
A Mathematician's Miscellany'').
E. T. Whittaker was his only official student. ==Family==