 In this example, we are dealing with a determinate problem, i.e., a problem to which there are a finite number of solutions, and we can therefore reduce the problem to a single equation that expresses the unknown quantity in terms of the known quantities. However, as Descartes points out, there are also indeterminate problems that involve an infinite number of solutions. (Locus problems, such as the Pappus Problem, are of this sort, because the solution includes the infinitely many points that lie along a curve.) When dealing with an indeterminate problem, Descartes instructs us that “we may arbitrarily choose lines of known length for each unknown line to which there corresponds no equation” (G, 9), i.e., we are to set the unknown lines as oblique coordinates that have a stated value. We then generate several equations that express the unknown quantities in terms of one or more known quantities, and solve the equations simultaneously. This is precisely the approach that Descartes takes as he treats the Pappus Problem in Book One.