Calculus

“calculus of infinitesimals”, study of continous change

study of rates ath which quantities change.

Example of a straigth line $y=mx+b$, $m=\Delta y / \Delta x$

“Differentialquotient”:

$m = \lim_{x_1 -> x_0} \frac{f(x_1) - f(x_0)}{x_1 - x_0}$

$f'(x) = \frac{d}{dx} f(x) = \lim_{h -> 0} \frac{f(x + h) - f(x)}{h}$

$f''(x) = \frac{d^2}{dx^2} f(x)$

Geometrically, derivative of f at point x=a is slope of tangent line.

Relation between collection of functions and their derivatives.

Ordinary differential equation:

Differential operator

$f'(x)=f(x)^2 * x$

$\frac{dy}{dx} = y^2 * x$

$dy = y^2 * x {dx}$

$\frac{1}{y^2} dy = x {dx}$

$\int \frac{1}{y^2} dy = \int x {dx}$

$-y^{-1} + c_1 = 1/2 x^2 + c_2$

$-(1/y) = 1/2 x^2 + c_2 - c_1$ $(c_2 - c_1 = c)$

$y = \frac{-1}{(1/2 x^2 + c)}$