Sum of Trigonometric Ratios in Terms of Their Product
cos4x+cos3x+c...
Question
cos4x+cos3x+cos2xsin4x+sin3x+sin2x is equal to -
A
cot3x
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B
cos3x
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C
tan3x
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D
None of these
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Solution
The correct option is Acot3x cos4x+cos3x+cos2xsin4x+sin3x+sin2x =(cos4x+cos2x)+cos3x(sin4x+sin2x)+sin3x =2cos3xcosx+cos3x2sin3xcosx+sin3x =cos3x[2cosx+1]sin3x[2cosx+1] =cot3x