General solutions (1 Viewer)

cutemouse · Jul 30, 2009

$cos4\theta + cos2\theta = \sqrt2cos^2\theta + \frac{1}{\sqrt2}sin2\theta$

Thanks =D

Timothy.Siu · Jul 30, 2009

jm01 said:
$cos4\theta + cos2\theta = \sqrt2cos^2\theta + \frac{1}{\sqrt2}sin2\theta$

Thanks =D

LHS= 2cos 3@cos@
RHS=root2(cos^2 @)+2/root2 . sin@cos@
=root2cos@(cos@+sin@)
=root2cos@(root2cos(@-pi/4)
=2cos@cos(@-pi/4)

cos@(cos3@-cos(@-pi/4))=0
cos@=0 or cos3@=cos(@-pi/4)
not really sure how to do it.

untouchablecuz · Jul 31, 2009

cos3x = cos(x-pi/4)

3x = 2kpi - (x-pi/4) or 3x = 2kpi + (x-pi/4)

i.e x = (pi/4)(2k + 1/4) or x = (pi/2)(2k - 1/4)

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General solutions (1 Viewer)

cutemouse

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Timothy.Siu

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untouchablecuz

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