The ancient Greeks certainly used calculus. Archimedes used regular polygons inscribed and circumscribing a circle to estimate the value of pi. The perimeter of the circle (the circumference) lay between the perimeters of the two sets of polygons. The limit, as the number of sides of the polygon were increased, gave pi. Unfortunately, calculations of trigonometric ratios were not sufficiently refined for Archimedes to get very accurate results.
Notable are Gaston Julia, for whom the Julia fractal is named (the Mandelbrot fractal is the most famous kind of the Julia fractal), and Jyeshtadeva, an Indian mathematician who lived in the 1500s and was influential in developing an Indian version of calculus many years before the West discovered calculus.
This kind of number is called "irrational", meaning (to a mathematician!) "not a ratio."
Pre calculus, calculus and beyond.... you will have to acquire these courses before you get to become a pediatrician
calculus
One uses calculus including differential equations and vector calculus in the undergrad courses which is as far as got.
Algebra, Trigonometry, Calculus, Geometry.
Pasta can be analogous to a kind of "knot theory."
Pretty much everything can be applied to calculus, and calculus to everything. If you have ever read the novel "Halo" you can see (in the first book) that Master Chief, had forgotten how much gravity was on the space-craft, and used calculus to determine the acceleration of gravity by timing the drop of a bolt and figuring out everything else. Calculus is especially important for any kind of profession that involves projectiles.
Calculus is a very wide ranging subject, which is not really possible to generalise (particularly since you do not indicate what kind of level of calculus you wish summarised- e.g beginners, intermediate, post-grad etc...)
He became a mathematician by studying math. He believed that numbers and math held the secrets of the universe. He tried to explain everything he observed with some kind of mathematical formula.
It can vary..you can get a undergraduate/graduate major ,masters, bachelors or a Ph.D
Very hard. Only the most skilled mathematician can divide by potato.