cos 4x * cos x + sin 4x * sin x = 1/2 Find x.. please and ty.

Juliaan Member Joined Apr 30, 2008 Messages 92 Gender Male HSC 2009 Feb 23, 2009 #1 cos 4x * cos x + sin 4x * sin x = 1/2 Find x.. please and ty.

Trebla Administrator Administrator Joined Feb 16, 2005 Messages 7,829 Gender Male HSC 2006 Feb 23, 2009 #2 I'm assuming you do Ext1, so: cos 4x. cos x + sin 4x. sin x = 1/2 cos (4x - x) = 1/2 cos 3x = 1/2 ....and solve away.....lol

I'm assuming you do Ext1, so: cos 4x. cos x + sin 4x. sin x = 1/2 cos (4x - x) = 1/2 cos 3x = 1/2 ....and solve away.....lol

madsam God among men Joined Feb 16, 2008 Messages 250 Gender Male HSC 2009 Feb 23, 2009 #3 cos4x cosx + sin4x sinx =1/2 cos (4x - x) = 1/2 cos (3x) = 1/2 3x = pi/3 x = pi/6 OR 3x = 5pi/3 x = 5pi/6 OR 3x = pi/3 + 2pi 3x = 7pi/3 x = 7pi/6 OR 3x = 4pi - pi/3 x = 11pi/6 assuming 0< x < 2pi

cos4x cosx + sin4x sinx =1/2 cos (4x - x) = 1/2 cos (3x) = 1/2 3x = pi/3 x = pi/6 OR 3x = 5pi/3 x = 5pi/6 OR 3x = pi/3 + 2pi 3x = 7pi/3 x = 7pi/6 OR 3x = 4pi - pi/3 x = 11pi/6 assuming 0< x < 2pi

Juliaan Member Joined Apr 30, 2008 Messages 92 Gender Male HSC 2009 Feb 23, 2009 #4 I don't personally do ext 1, though my mate does, and thanks alot guys ~ (doesn't have a BoS, though i'll mention you's haha)

I don't personally do ext 1, though my mate does, and thanks alot guys ~ (doesn't have a BoS, though i'll mention you's haha)