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DoNoT SpAm!
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manjitdas221:
te amo
Answers
Answered by
5
Step-by-step explanation:
LHS:
cos 4A
= cos(2.2A)
= 2 cos² (2A) - 1
= 2(2 cos² 2A - 1)² - 1
= 2(4 cos⁴ A - 4 cos² A + 1) - 1
= 8 cos⁴ A - 8 cos² A + 1
RHS
Hope it helps!
:-)
i didn't understand last 2nd step.. can u elaborate plz?
(a - b)^2 = a^2 + b^2 - 2ab. Here a = 2cos2A, = 1
Any doubts?
thn it shud be 4cos^2A - 4cos2A +1..
Mistake... Let me correct
sure :)
Done. Thanks
Did u understand the answer?
yes.. tnx
Answered by
1
cos (4A) = cos (2•(2A))
↔ cos (2•(2A)) = 2•cos² (2A) - 1
↔ cos (4A) = 2•cos² (2A) - 1
↔ cos (4A) = 2•(2•cos² A - 1)² - 1
↔ cos (4A) = 2•(2•cos² A - 1)² - 1
↔ cos (4A) = 2•{4•(cos² A)² - 4•(cos² A) + 1} - 1
↔ cos (4A) = 8•cos⁴ A - 8•cos² A + 2 - 1
↔ cos (4A) = 8•cos⁴ A - 8•cos² A + 1
↔ cos (4A) = 1 - 8•cos² A + 8•cos⁴ A .... qid
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