CBSE Class 10 Answered
prove the following
Asked by sunil_0010 | 01 Nov, 2009, 04:03: PM
Expert Answer
(cos8θ-sin8θ) = (cos4θ-sin4θ)(cos4θ+sin4θ)
= (cos2θ-sin2θ)(cos2θ+sin2θ)(cos4θ+sin4θ)
= (cos2θ-sin2θ)(cos4θ+sin4θ)
= (cos2θ-sin2θ)(cos4θ+sin4θ)..............(1)
Now (cos2θ+sin2θ)2 =cos4θ+ 2sin2θcos2θ + sin4θ
1 = cos4θ+ 2sin2θcos2θ + sin4θ
cos4θ+sin4θ = 1 - 2sin2θcos2θ.............using this result in (1).
(cos8θ-sin8θ) = (cos2θ-sin2θ)(1 - 2sin2θcos2θ)
Regards,
Team,
TopperLearning.
Answered by | 01 Nov, 2009, 10:42: PM
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