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cos((2pi)/(7))+cos((4pi)/(7))+cos((6pi)/...

`cos((2pi)/(7))+cos((4pi)/(7))+cos((6pi)/(7))=`

A

1

B

`-1`

C

`(1)/(2)`

D

`-(1)/(2)`

Text Solution

Verified by Experts

The correct Answer is:
D
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KUMAR PRAKASHAN-TRIGONOMETRIC FUNCTIONS -TEXTBOOK BASED MCQS
  1. cos^(2)(7(1^@)/(2))-cos^(2)(37(1^(@))/(2))= …………

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  2. The value of cos(480^(@))sin(150^(@))+sin(600^(@))cos(390^(@)) is …………...

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  3. cos((2pi)/(7))+cos((4pi)/(7))+cos((6pi)/(7))=

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  4. If (tanx)/(1)=(tany)/(2)=(tanz)/(3)(ne0)andx+y+z=pi then which of the ...

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  5. cos((pi)/(7))cos((2pi)/(7))cos((4pi)/(7))= ………..

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  6. sin((pi)/(16))sin((3pi)/(16))sin((5pi)/(16))sin((7pi)/(16))= ………..

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  7. cos^(2)((pi)/(12))+cos^(2)((3pi)/(12))+cos^(2)((5pi)/(12))= …………

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  8. If A=125 and x=sinA^(@)+cosA^(@) then ………..

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  9. The value of sqrt(3)cosec20^(@)-sec20^(@) is …………

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  10. If cosalpha=-(4)/(5),(pi)/(2)ltalphaltpi then tan((alpha)/(2))= ……….

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  11. If tanx=-(4)/(3),(pi)/(2)ltxltpi then sin((x)/(2))= …………

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  12. One of the roots of 4x^(3)-3x=(1)/(2) is ………

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  13. The value of cos(67(1^(@))/(2)) is ………….

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  14. If one of the roots of 25cos^(2)theta+5costheta-12=0 is alpha then the...

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  15. If cosalpha=-0.6andpiltalphalt(3pi)/(2) then tan((alpha)/(4)) = ………..

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  16. If tanx=(b)/(a) then acos(2x)+bsin(2x) = ……….

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  17. If cosA=(3)/(4) then 32sin((A)/(2))sin((5A)/(2)) = ……………

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  18. sqrt(2+sqrt(2+2cos4theta))= …………

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  19. If tan^(2)theta=2tan^(2)phi+1 then the value of cos(2theta)+sin^(2)phi...

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  20. If tan""(alpha)/(2)andtan""(beta)/(2) are roots of the equation 8x^(2)...

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