find the general solution of cos4x = cos2x
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cos4x=cos2(2x)=2cos2xsin2x
then
cos4x=cos2x
or 2cos2xsin2x=cos2x
or 2sin2x =1
or sin2x =1/2
or sin2x =sin45°
.: 2x=45
or x=45/2
or x= 22*1/2
then
cos4x=cos2x
or 2cos2xsin2x=cos2x
or 2sin2x =1
or sin2x =1/2
or sin2x =sin45°
.: 2x=45
or x=45/2
or x= 22*1/2
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