Cos 3x+ cos x - 2cos2x=0
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Answer:
-4cos2xsin(x/2)^2
Step-by-step explanation:
Cos3x+cosx-2cos2x
2cos((3x+x)/2)cos((3x-x)/2)-2cos2x
2cos2xcosx-2cos2x
2cos2x(cosx-1)
2cos2x(1-2sin(x/2)^2-1)
2cos2x(-2sin(x/2)^2)
-4cos2xsin(x/2)^2
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