Question
3[sin4(3π2−α)+sin4(3π+α)] - [sin6(π2+α)+sin6(5π−α)] =
Answer: Option B
:
B
(b) 3[sin4(3π2−α)+sin4(3π+α)] - [sin6(π2+α)+sin6(5π−α)]
=3(−cosα)4+(−sinα)4−2cos6α+sin6α
=3(cos2α+sin2α)2−2sin2αcos2α−2(cos2α+sin2α)3−3sin2αcos2α(cos2α+sin2α)
=3−6sin2αcos2α−2+6sin2αcos2α=3−2=1
Trick: Put α=0 , the value of expressions remains 1 i.e., it is independent of α
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:
B
(b) 3[sin4(3π2−α)+sin4(3π+α)] - [sin6(π2+α)+sin6(5π−α)]
=3(−cosα)4+(−sinα)4−2cos6α+sin6α
=3(cos2α+sin2α)2−2sin2αcos2α−2(cos2α+sin2α)3−3sin2αcos2α(cos2α+sin2α)
=3−6sin2αcos2α−2+6sin2αcos2α=3−2=1
Trick: Put α=0 , the value of expressions remains 1 i.e., it is independent of α
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