Wallis was able to discover this, while he was trying to figure out the integral of (1-x2)1/2 from 0-1, used to find the area of a circle of unit radius. Using Cavalieri's ideas on indivisibles, Wallis resolved the issue of integrating (1-x2)n for integer powers of n. However, incapable of dealing with fractional powers, he used interpolation, which was a word Wallis introduced to the world of mathematics within this work. His method of interpolation developed from a combination of Kepler's idea of continuity, as well as his discovered techniques on evaluating integrals (McElroy). Shortly after, in 1659, Wallis published another tract that included the answer to the problems of the cycloid, which had originally been brought forth by Pascal. In this tract, he also, by chance, explained how his principles from his Arithmetica Infinitorum could be used for reflecting algebraic curves. He also came up with a solution to the issue of adjusting "the semi-cubical parabola x³ = ay²" (Ball), which had earlier been discovered by William Neil, in