Considering the given identities 1. sin4θ−sin2θ=cos4θ−cos2θ ⇒sin2θ(sin2θ−1) =cos2θ(cos2θ−1) ⇒sin2θ(−cos2θ)=cos2θ(−sin2θ) [∵sin2A+cos2A=1] ⇒−sin2θ⋅cos2θ=−sin2θ⋅cos2θ Which is true. 2. sin4θ+cos4θ=1+2sin2θcos2θ LHS =(sin2θ)2+(cos2θ)2 =(sin2θ+cos2θ)2 −2sin2θ⋅cos2θ [∵a2+b2=(a+b)2−2ab] =1−2sin2θ⋅cos2θ ≠ R.H.S. 3. tan4θ+tan2θ=sec4θ−sec2θ ⇒tan2θ(tan2θ+1) =sec2θ(sec2θ−1)⇒tan2θ⋅sec2θ=sec2θ⋅tan2θ [∵1+tan2A=sec2A] Which is true. Hence, 1 and 3 are the identities.