determine the maximum and minimum values of the function y=2cos2x-cos4x

Dear Student,

 

2cos2x-cos4x

 

=2 cos2x -2cos22x +1

 

=-2(cos2x-1/2)2 +3/2

 

minimum value occur when cos2x-1/2 will be maximum

 

  =-2(-1-1/2)2 +3/2

 

  =-3
and minimum value is 3/2
Regards
 

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