What is the value of sin (90o + 2A)[4 – cos2 (90o – 2A)]?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. 4(cos6 A – sin6 A)
sin (90o + 2A)[4 – cos2 (90o – 2A)]
= cos2A[4 - sin22A]
= 4(cos2A - sin2A)(cos4A + sin4A + cos2Asin2A)
= 4(cos6 A – sin6 A)