Further Trig.. (1 Viewer)

[Juliaan]

cos 4x * cos x + sin 4x * sin x = 1/2

Find x..

please and ty.

 

[Trebla]

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]

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]

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)