Matthew Stewart (mathematician)

[1][2] He was born in the manse at Rothesay, on the Isle of Bute, on 15 January 1717,[3] the son of Rev Dugald Stewart, the local minister, and his wife, Janet Bannantyne.

A close friendship developed between Simson and Stewart, in part because of their mutual admiration of Pappus of Alexandria, which resulted in many curious communications with respect to the De Locis Planis of Apollonius of Perga and the Porisms of Euclid over the years.

[5] This correspondence suggests that Stewart spent several weeks in Glasgow starting May 1743 assisting Robert Simson in the production of his Apollonii Pergaei locorum planorum libri II, which was published in 1749.

[6] This book extended some ideas of Robert Simson and is best known for proposition II, or what is now known as Stewart's theorem, which relates measurements on a triangle to an additional line through a vertex.

In 1772 his health began to deteriorate and his duties as professor at Edinburgh were initially shared, then taken over by, his son Dugald Stewart, who later became a prominent Scottish philosopher.