Learning & Reasoning/Math Revisit

Single Variable 미적분 토막 연습

이현봉 2016. 4. 12. 03:52

ref:

Wiki: https://en.wikipedia.org/wiki/Lists_of_integrals#Lists_of_integrals

Differentiation Rules : https://en.wikipedia.org/wiki/Differentiation_rules



■ graphs of exponential functions f(x) = ax , a > 0.  Then f(x) is a continuous function with domain R, and range (0, ∞), and f(x) > 0 for all x.   



When x, y are real numbers, and a, b > 0

what is 'e'?

{\displaystyle {\frac {d}{dx}}\left(c^{ax}\right)={ac^{ax}\ln c},\qquad c>0} 


* derivative of an exponential function is proportional to the function itself. 


{\displaystyle {\begin{aligned}{\frac {d}{dx}}a^{x}&=\lim _{h\to 0}{\frac {a^{x+h}-a^{x}}{h}}=\lim _{h\to 0}{\frac {a^{x}a^{h}-a^{x}}{h}}\\&=a^{x}\cdot \left(\lim _{h\to 0}{\frac {a^{h}-1}{h}}\right).\end{aligned}}}

What is a base 'a' of the function f(x) = ax  so that f'(x) = f(x). It will make differentiation very nice looking.

e is that number.  e is an irrational number about 2.71818

So, of all the possible exponential functions f(x) = athat pass (0, 1), the function f(x) = ex is the one whose derivative value(slope) at x=0 is 1.  Because ex's derivative is ex itself, its height is its slope. 

ex)



ex)



■  Log Functions

 






■  Derivatives of Log Functions


since

example)


--------

Thus f'(x) = 1/x for all x 0


■  Derivatives and Integrations 


ex) Differentiate y using log differentiations

 

taking ln's to both sides,

Differentiating implicitely w.r.t. x,

 


ex)  y = f(x)g(x)  형태의 미분은

(f^{g})'=\left(e^{g\ln f}\right)'=f^{g}\left(f'{g \over f}+g'\ln f\right),\quad

Since 

예) 

또는,

하여

  (f^{g})'=\left(e^{g\ln f}\right)'=f^{g}\left(f'{g \over f}+g'\ln f\right),\quad

에 대입