"However, those precise trigonometric values were calculated by Indian mathematicians using infinite series expansions (today called “Taylor's” expansion, “Leibniz” series, etc.), and sophisticated techniques to sum infinite series. These techniques were not comprehended by European mathematicians (who were, then, still struggling at the level of decimal fractions introduced by Stevin, only in 1582). The key difficulty was with the notion of infinite sums, as in the non-terminating, non- recurring decimal expansion for the number pi. The notion of infinity brought religious beliefs prominently into play."