SIII - 20
8. (i) sint x = cos4 x = 1 - 2 cos2 x
(iii) sinó x + cos6 x = 1 - 3 sin2 x cos2 x.
Hint. (iii) a3 + b3 = (a + b)3 – 3 ab (a + b)
Answers
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Answer:
1 + cos 2x + cos 4x + cos 6x = ... 1+cos2x+cos4x+cos6x= A. 2cosxcos2x cos3x. B. 2cosxsin2xcos3x. C. 4cosxcos2xcos3x. D. 4cosxsin2xsin3x.
Step-by-step explanation:
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Answered by
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Step-by-step explanation:
1+cos2x+cos4x+cos6x=(1+cos2x)+(cos4x+cos6x)
=2cos
2
x+2cos5xcosx (∵cosA+cosB=2cos
2
A+B
cos
2
A−B
,cos2A=2cos
2
A−1)
=2cosx(cosx+cos5x)
=2cosx(2cos2xcos3x)
=4cosxcos2xcos3x
this one is one example like this process you can do
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