<PRE><B>Question 1112195</B>
cos 2 x + 3 cos x =1
2cos^2 x -1+3 cos x=1
2 cos^2x+3 cos x -2=0
(2 cos x-1)(cos x +2)=0
2 cos x=1  (cos x cannot be -2)
cos x= (1/2)
x=pi/3, 5 pi/3  ANSWER
cos 2 pi/3+ 3 cos pi/3=-0.5+3(0.5)=1
cos  10 pi/3+ 3 cos 5 pi/3=-0.5+3(0.5)=1
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