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The numerical value of cos 2pi/7 + cos 4...

The numerical value of `cos 2pi/7 + cos 4pi/7 + cos 6pi/7` is=........

A

`(1)/(2)`

B

0

C

`-(1)/(2)`

D

1

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A, B
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ADVANCED MATHS BY ABHINAY MATHS ENGLISH-TRIGONOMETRY -EXERCISES (Multiple Choice Questions)
  1. 7cosectheta+24sectheta=25cosecthetasectheta, then costheta=?

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  2. If 8sectheta+6cosectheta=20, then cottheta=?

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  3. The numerical value of cos 2pi/7 + cos 4pi/7 + cos 6pi/7 is=........

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  4. cos15^(@)cos7""(1)/(2)""^(@).cos82""(1)/(2)""^(@)=?

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  5. tan^(2)theta=1-e^(2), then sectheta+tan^(3)theta.cosectheta=?

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  6. 3tanthetatanphi=1, then (cos(theta-phi))/(cos(theta+phi))=?

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  7. tan20^(@)+tan40^(@)+sqrt(3)tan20^(@).tan40^(@)=?

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  8. sin36^(@).sin72^(@).sin108^(@).sin144^(@)=?

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  9. (2cos40^(@)-cos20^(@))/(sin20^(@))=?

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  10. The point (4,3) is translated to the point (3,1) and then the axes ar...

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  11. (cosx)/(cosy)=n,(sinx)/(siny)=m, then (m^(2)-n^(2))sin^(2)y=?

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  12. If xcostheta+ysintheta=4&xcostheta-ysintheta=0, then which one is corr...

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  13. If tan^(2)theta+cot^(2)theta=14, then sectheta.cosectheta=?

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  14. If cos(alpha+beta)=(4)/(5) and sin(alpha-beta)=(5)/(13) , where alpha ...

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  15. If tantheta-tanphi=xandcotphi-cottheta=y, then cot(theta-phi)=?

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  16. If 3costheta=5sintheta, then ((5sintheta-2sec^(3)theta+2costheta)/(5si...

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  17. sectheta+tantheta=2+sqrt(5), then sintheta will be

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  18. If 3tantheta+4=0 where (pi)/(2)lt thetaltpi, then the value of 2cot th...

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  19. If (1+sinx)/(cosx)+(cosx)/(1+sinx)=4, then find x.

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  20. costheta(tantheta+2)(2tantheta+1)=?

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