
- taylor expansion: $f(x) approx f(x_0) + frac{f’(x_0)}{1!}(x-x_0) + frac{f’‘(x_0)}{2!}(x-x_0)^2 + …$
Single-variable calculus
Derivatives:
$frac{d}{dx}x^n = nx^{n-1}$
$frac{d}{dx}a^x = a^{x}ln(a)$
$frac{d}{dx}ln(x) = 1/x$
$frac{d}{dx}tan(x)= sec^2(x)$
$frac{d}{dx}cot(x)= -csc^2(x)$
$frac{d}{dx}sec(x)= sec(x)tan(x)$
$frac{d}{dx}csc(x)= -csc(x)cot(x)$
$int tan = ln|sec|$
$int cot = ln|sin|$
$int sec = ln|sec+tan|$
$int csc = ln|csc-cot|$
$int frac{du}{sqrt{a^2-u^2}} = sin^{-1}(frac{u}{a})$
$int frac{du}{usqrt{u^2-a^2}} = frac{1}{a}sec^{-1}(frac{u}{a})$
$int frac{du}{a^2+u^2} = frac{1}{a} tan^{-1}(frac{u}{a})$
Continuous: left limit = right limit = value
Differentiable: continuous and no sharp points / asymptotes
L’Hospital’s - for indeterminate forms: $(frac{f(x)}{g(x)})’ = frac{f’(x)}{g’(x)}$
Integration by parts: $int{udv}=uv-int{duv}$, LIATE
Expansions:
$e^x = sum{frac{x^n}{n!}}$
$sin(x) = sum_0^infty{frac{(-1)^n x^{2n+1}}{(2n+1)!}}$
$cos(x) = sum_0^infty{frac{(-1)^n x^{2n}}{(2n)!}}$
Geometric Sum: $a_{1st}frac{1-r^{n+1}}{1-r}$
Multivariable calculus
- Polar: r,$theta$,z
- Spherical: $rho,theta,phi$
- Clairut’s Thm: Conservative function $f_{xy}=f_{yx}$
- Lagrangian - solves minimize f subject to g = c
- solution will always be tangent to f
- $nabla f = lambda nabla g$ - gives us n constraints
- remember g = c is a constraint too
- to do this efficiently, define the Lagrangian $L(x, lambda) = f - lambda cdot g$
- taking deriv wrt $lambda$ and setting = 0 enforces g = c
- taking deriv wrt other variables and setting = 0 enforces other conditions
- therefore final eq just becomes $nabla L = 0$




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