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Conics Problem (1 Viewer)

Thread starter nrumble42
Start date Dec 8, 2016

N

nrumble42

Member

#1

The point Q is (3cos(ϴ + ∏/2), 2sin(ϴ + ∏/2)).

How does this equal (-3sinϴ, 2cosϴ)?

Any help would be great thanks

L

Lugia101101

New Member

#2

$\text{The graph of }\cos{\theta}\text{ is simply that of }\sin{\theta}\text{ shifted }\frac{\pi}{2}\text{ units to the left.}$
$\begin{align*}\text{So as }\sin{(\theta+a)}\text{ shifts the graph of }\sin{\theta}\text{, }a\text{ units to the left, }\sin{(\theta+\frac{\pi}{2})}=\cos{\theta}\text{.}\end{align*}$
$\text{Now }\cos{(\theta+\frac{\pi}{2})}\text{ is then }\sin{(\theta+\frac{\pi}{2}+\frac{\pi}{2})}=\sin{(\theta+\pi)}=-\sin{\theta}$

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