Prove the following with the help of identities:
sin8θ – cos8θ = (sin2θ – cos2θ) (1– 2sin2θ cos2θ)
Taking L.H.S we get,
Sin8 θ– cos8 θ
Using the formula: a2 – b2 = (a – b)(a + b)
⇒ (sin4 θ – cos4 θ)(sin4 θ + cos4 θ)
⇒ (sin2 θ – cos2 θ)(sin2 θ + cos2 θ)((sin2 θ + cos2 θ)2 – 2.sin2 θ.cos2 θ)
⇒ (sin2 θ – cos2 θ)(1)((1)2 – 2.sin2 θ.cos2 θ) (Using: sin2 θ + cos2 θ = 1.)
⇒ (sin2 θ – cos2 θ)(1 – 2.sin2 θ.cos2 θ)
= R.H.S
Hence, proved
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