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Question

If sinx + sin2x = 1 then the value of cos12x + 3cos10x + 3cos8x + cos6x + 1 is equal to

A
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B
1
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C
3
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D
2
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Solution

The correct option is B 1
Given: sinx+sin2x=1
sinx=1sin2x=cos2x
Now,
cos12x+3cos10x+3cos8x+cos6x
(cos4x)3+3(cos4x)2cos2x+3cos4x(cos2x)2+(cos2x)3
(sin2x)3+3sin4xcos2x+3sin2xcos4x+(cos2x)3
[sin2x+cos2x]3
13
1.

1230088_1315468_ans_c52c1db97bf343a1b479e46bb05a3046.jpg

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