If cos2Θ – sin2Θ = x, then 1 + cos4Θ – sin4Θ = ?
সমাধান
সঠিক উত্তর: Option C
We know,
cos²Θ + sin²Θ = 1
and, cos2Θ - sin2Θ = x
Now, (cos²Θ + sin²Θ) × (cos²Θ - sin²Θ) = 1 × x
⇒ cos4Θ - sin4Θ = x
⇒ 1+ cos4Θ - sin4Θ = 1+ x = x + 1