MHB -7.8.98 amplitude period PS VS graph. of cos eq

AI Thread Summary
The discussion focuses on determining the amplitude, period, phase shift (PS), and vertical shift (VS) for the function y = -3cos(xπ/2) + 2. The amplitude is identified as 3, the vertical shift as 2, and the period is calculated to be 4 using the formula T = 2π/(ω - φ), with ω determined to be π/2 and φ as 0. Participants also discuss graphing the function using TikZ, with some initial attempts at creating the graph. Overall, the conversation emphasizes the calculations and graphical representation of the cosine function based on the provided parameters.
karush
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Find amplitude, period, PS, VS. then graph.

$[DESMOS]{"version":7,"graph":{"viewport":{"xmin":-10,"ymin":-11.610693119544644,"xmax":10,"ymax":11.610693119544644}},"randomSeed":"996fd79a7f16736ddbff1ce2310a2f50","expressions":{"list":[{"type":"expression","id":"1","color":"#c74440","latex":"y=-3\\cos\\left(\\frac{k \\pi}{2}\\right)+2"}]}}[/DESMOS]$

ok I think these are the plug ins we use
$Y_{cos}=A\cos\left[\omega\left(x-\dfrac{x \phi}{\omega} \right)\right]+B
\implies A\cos\left(\omega x-\phi\right)+B
\implies T=\dfrac{2\pi}{\omega}
\implies PS=\dfrac{\phi}{\omega}$

ok I wanted to do the graph in tikx but was just looking for an pre done one as an example to fit this eq
 
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$y = A\cos[(\omega-\phi)x] + B$

$T = \dfrac{2\pi}{\omega-\phi}$

$PS = 0$
 
skeeter said:
$y = A\cos[(\omega-\phi)x] + B$

$T = \dfrac{2\pi}{\omega-\phi}$

$PS = 0$
$y=-3\cos\left(\dfrac{x\pi}{2}\right)+2$
so from observation A=|-3|=3 and B=2
$T = \dfrac{2\pi}{\omega-\phi}$
ok I am ? what is $\omega -\phi$

W|A says period is 4

i started a tikz no sure how to transform it ...
$\begin{tikzpicture}[xscale=.5,yscale=.5]
[help lines/.style={black!50,very thin}] \draw[->,thin] (-6,0)--(6,0) node[above] {$x$};
\draw[->,thin] (0,-1)--(0,4) node[above] {$f(x)=sin\ x$};
\node [below] at (-2*3.1416,0) {-2$\pi$};
\node [below] at (-1*3.1416,0) {-$\pi$};
\node [below] at (1*3.1416,0) {$\pi$};
\node [below] at (2*3.1416,0) {2$\pi$};
\draw[very thick,color=red] plot [domain={-360/90}:{360/90},smooth] (\x,{sin(90*\x)});
\end{tikzpicture}$
 
Last edited:
karush said:
$y=-3\cos\left(\frac{x\pi}{2}\right)+2$
so from observation A=|-3|=3 and B=2
$T = \dfrac{2\pi}{\omega-\phi}$
ok I am ? what is $\omega -\phi$

W|A says period is 4

$B = (\omega - \phi) = \dfrac{\pi}{2} \implies T = 4$

note $\phi = 0$ for $y=-3\cos\left(\frac{\pi}{2} \cdot x \right)+2$
 
skeeter said:
$B = (\omega - \phi) = \dfrac{\pi}{2} \implies T = 4$

note $\phi = 0$ for $y=-3\cos\left(\frac{\pi}{2} \cdot x \right)+2$

so then $\omega=\dfrac{\pi}{2}$
 
karush said:
so then $\omega=\dfrac{\pi}{2}$

yes, and $\phi = 0$
 
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