SOLUTION: 2cos2x = 4cosx - 3, 0<= x <= 360
Hi, I'm stuck on this trig question I've tried substituting in a few things but they just dont seem to work... :/
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Question 760485: 2cos2x = 4cosx - 3, 0<= x <= 360
Hi, I'm stuck on this trig question I've tried substituting in a few things but they just dont seem to work... :/
Answer by Cromlix(4381) (Show Source): You can put this solution on YOUR website!
2cos2x = 4cosx - 3
2(2cos^2x - 1) = 4cosx - 3
4cos^2x - 2 = 4cosx - 3
4cos^2 x - 4cosx + 1 = 0
(2cosx - 1)(2cosx - 1) = 0
2cosx - 1 = 0
2cosx = 1
cosx = 1/2
x = 60 degs and 300 degs
Hope this helps.
:-)
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