|Description||The ‘French’ or ‘Parisian’ problem, as set by François Dulaurens, the author of Specimina mathematica (1667). The problem was presented at the meeting of the Royal Society on 12 December 1667, and forwarded to John Collins, William Brouncker and John Wallis. |
The problem, as understood by Wallis, was as follows: 'given in number the circle CBD with radius CB, and the inscribed line BD protracted as far as may be desired beyond the circle, yet so that BY drawn parallel to CF may cut the circle in Y. To find the true value of the line BY, not an approximation (which may easily be obtained from a table of sines)'.
In his letter to Wallis dated 24 December 1667, Henry Oldenburg mentioned that 'a certain person here' (identified by R. A. Hall and M. B. Hall as John Collins) had surmised that BY was a rational quantity, but had not offered a proof, since William Brouncker thought that GF might prove irrational. Wallis offered his proof that BY was rational in his letter to Oldenburg dated 8 February 1668.