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If cos x + cos y = a, cos 2x + cos 2y =b...

If `cos x + cos y = a, cos 2x + cos 2y =b, cos 3x + cos 3y =c`, then

A

`cos^(2) x + cos^(2) y = 1+ ( b)/( 2)`

B

`cos x cosy = ( a^(2))/( 2) - (( b+2)/( 4))`

C

`2a^(3) + c = 3a ( 1+b)`

D

`a+b+c = 3abc`

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The correct Answer is:
A, B, C
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ML KHANNA-TRIGONOMETRY RATIOS AND IDENTITIES-PROBLEM SET (4) ( MULTIPLE CHOICE QUESTIONS)
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