삼각함수,trigonometric_function


Sub:
삼각함수의_극한
삼각치환,trig_substitution

$\displaystyle \sin$ $\displaystyle \csc$
$\displaystyle \cos$ $\displaystyle \sec$
$\displaystyle \tan$ $\displaystyle \cot$

sine_function WtEn:sine_function Ggl:sine function
cosine_function WtEn:cosine_function Ggl:cosine function
tangent_function WtEn:tangent_function Ggl:tangent function
cotangent_function WtEn:cotangent_function Ggl:cotangent function
secant_function WtEn:secant_function Ggl:secant function
cosecant_function WtEn:cosecant_function Ggl:cosecant function

or

사인,sine
코사인,cosine
탄젠트,tangent ....?

rel sinusoid / sinusoidal_function 이었나? spell chk.



1. 삼각함수 미분표

(sin x)' = cos x (csc x)' = - csc x cot x
(cos x)' = - sin x (sec x)' = sec x tan x
(tan x)' = sec² x (cot x)' = - csc² x

$\displaystyle \frac{d}{dx}\sin x$$\displaystyle \cos x$ $\displaystyle \frac{d}{dx}\csc x$$\displaystyle -\csc x \cot x$
$\displaystyle \frac{d}{dx}\cos x$$\displaystyle -\sin x$ $\displaystyle \frac{d}{dx}\sec x$$\displaystyle \sec x \tan x $
$\displaystyle \frac{d}{dx}\tan x$$\displaystyle \sec^2 x$ $\displaystyle \frac{d}{dx}\cot x$$\displaystyle -\csc^2 x$

줄이 안맞아서 다른 방식으로.

$\displaystyle !mimetex $$\huge\begin{array}{|rl|rl|} \hline \frac{d}{dx}\sin x &= \cos x & \frac{d}{dx}\csc x &= -\csc x \cot x\\ \hdash \frac{d}{dx}\cos x &= -\sin x & \frac{d}{dx}\sec x &= \sec x \tan x \\ \hdash \frac{d}{dx}\tan x &= \sec^2 x & \frac{d}{dx}\cot x &= -\csc^2 x \\ \hline\end{array}$$

2. 삼각함수 미분 증명

3. 삼각함수 적분


4. 삼각함수 극한

$\displaystyle \lim_{x\to0}\frac{\sin x}x=1$
이것은 보통 squeeze theorem으로 증명. 로피탈로도 가능.
넓이 부등식을...
$\displaystyle \frac12\cos x\sin x<\frac{x}2<\frac12\tan x$
$\displaystyle \cos x<\frac{x}{\sin x}<\frac{1}{\cos x}$
$\displaystyle \cos x<\frac{\sin x}{x}<\frac{1}{\cos x}$
$\displaystyle \lim_{x\to 0}\cos x<\lim_{x\to 0}\frac{\sin x}{x}<\lim_{x\to 0}\frac{1}{\cos x}$

$\displaystyle \lim_{x\to0}\frac{\cos x-1}{x}=0$