If cos2theta -sin2theta=1/3, value of (cos4theta-sin4theta+1) is:

(A) 4/3

(B) 5/3

• cos²2@ +sin²2@ =1
  
  (cos2@-sin2@ )²+ 2sin2@cos2@ =1
  
  1/9 +sin4@ =1
  
  sin4@= 1-1/9 = 8/9
  
  cos4@ = root of (1- 64/81) = root 17/9
  
  cos4@-sin4@+1 = root 17/9 -8/9 +1
  
  =(root 17 +1)/9
• 12 years agoHelpfull: Yes(0) No(0)