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trig question (1 Viewer)

Thread starter darkphoenix
Start date Sep 19, 2012

D

darkphoenix

Member

#1

cos5x=cos2x (2marks)
find the general solution for x?
don't really get it, can anyone explain? thx

A

Aykay

Member

#2

$cos(5x) = cos(2x)\\ \\ \text{using the general solution:} \\ \\ 5x = 2n\pi \ \pm \ 2x \\ \\ \therefore 7x= 2n\pi \ \ or \ 3x = 2n\pi \\ \\ so \ x = \frac{2n\pi}{7} \ or \ x = \frac{2n\pi}{3}$

D

darkphoenix

Member

#3

Aykay said:
$cos(5x) = cos(2x)\\ \\ \text{using the general solution:} \\ \\ 5x = 2n\pi \ \pm \ 2x \\ \\ \therefore 7x= 2n\pi \ \ or \ 3x = 2n\pi \\ \\ so \ x = \frac{2n\pi}{7} \ or \ x = \frac{2n\pi}{3}$

Great, thank you ！

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