From: Andrew Lorimer Date: Wed, 8 Aug 2018 05:08:25 +0000 (+1000) Subject: differentiation X-Git-Tag: yr11~73 X-Git-Url: https://git.lorimer.id.au/notes.git/diff_plain/a225a5d30844ad7f4d65c437aa9229fab409b84f differentiation --- diff --git a/spec/calculus.md b/spec/calculus.md index 28ca344..d1a981c 100644 --- a/spec/calculus.md +++ b/spec/calculus.md @@ -33,7 +33,39 @@ e.g. $$\lim_{x \rightarrow \infty}{{2x+3} \over {x-2}}={{2+{3 \over x}} \over {1-{2 \over x}}}={2 \over 1} = 2$$ - ## Continuous functions A function is continuous if $L^-=L^+=f(x)$ for all values of $x$. + +## Gradients of secants and tangents + +Secant (chord) - line joining two points on curve + +Tangent - line that intersects curve at one point + +given $P(x,y) \quad Q(x+\delta x, y + \delta y)$: +gradient of chord joining $P$ and $Q$ is ${m_{PQ}}={\operatorname{rise} \over \operatorname{run}} = {\delta y \over \delta x}$ + +As $Q \rightarrow P, \delta x \rightarrow 0$. Chord becomes tangent (two infinitesimal points are equal). + +Can also be used with functions, where $h=\delta x$. + +## First principles derivative + +$$\lim_{\delta x \rightarrow 0}{\delta y \over \delta x}={dy \over dx} = f^\prime(x)$$ + +$$m_{\operatorname{tangent}}=\lim_{h \rightarrow 0}f^\prime(x)$$ + + + +$$m_{\operatorname{chord PQ}}=f^\prime(x)$$ + +first principles derivative: +$${m_{\operatorname{tangent at P}} =\lim_{h \rigzhtarrow 0}}{{f(x+h)-f(x)}\over h}$$ + + + + +## Euler's number as a limit + +$$\lim_{h \rightarrow 0} {{e^h-1} \over h}=1$$