Question 24:
Prove that cos 4x = 1−8sin2 x cos2 x
Answer
L.H.S. = cos 4x
= cos 2(2x)
= 1 −2 sin2 2x [cos 2A = 1 − 2 sin2 A]
= 1 − 2(2 sin x cos x)2 [sin2A = 2sin A cosA]
= 1 − 8 sin2x cos2x
= R.H.S.
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Question 24:
Prove that cos 4x = 1−8sin2 x cos2 x
Answer
L.H.S. = cos 4x
= cos 2(2x)
= 1 −2 sin2 2x [cos 2A = 1 − 2 sin2 A]
= 1 − 2(2 sin x cos x)2 [sin2A = 2sin A cosA]
= 1 − 8 sin2x cos2x
= R.H.S.
Latest Govt Job & Exam Updates: