This is the title page of the Treatise of Algebra (1685), by John Wallis. This is probably the first attempt at a history of the subject of algebra, presented in the context of a text on the subject. Among the most famous parts of this treatise is Wallis's discussion of the work of Thomas Harriot, especially his contention that Rene Descartes plagiarized Harriot's symbolization procedure in algebra.
A set of four congruent circles whose centers form a square is inscribed in a right triangle ABC where C is the right angle and serves as one corner of the square. Find their radius in terms of the sides; a,b,c, of the triangle.