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Prove that: cos(pi/7)cos(2pi/7)cos(4pi/7...

Prove that: `cos(pi/7)cos(2pi/7)cos(4pi/7)=-1/8,`

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RD SHARMA ENGLISH-TRIGONOMETRIC RATIOS OF MULTIPLE AND SUBMULTIPLE ANGLES-All Questions
  1. Write the value of cos^2 76^@+cos^2 16^@- cos76^@ cos16^@

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  2. If (pi/4)< theta <(pi/2),then write the value of sqrt(1-sin2theta)

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  3. Prove that: cos(pi/7)cos(2pi/7)cos(4pi/7)=-1/8,

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  4. If sin x+cos x=a , find the value of sin^6x+cos^6xdot

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  5. If sin x+cos x=a , find the maximum and minimum value of a

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  6. 8*sin(x/8)*cos(x/2)*cos(x/4)*cos(x/8)=

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  7. Show that cos(pi/65)cos((2pi)/65)cos((4pi)/65)cos((8pi)/65)cos((16pi)/...

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  8. For all real values of x ,cotx-2cot2x is equal to a.tan2x b. t a n x c...

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  9. The value of 2tanpi/(10)+3secpi/(10)-\ 4cospi/(10) is 0 b. 1 c. sqrt(5...

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  10. If in a Delta ABC, tanA+tanB+tanC=6 then cotA cotB cot C= a.6, b. 1, c...

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  11. If sin alpha+sin beta=a\ a n d\ cosalpha-cosbeta=b , then tan(alpha-be...

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  12. The value of t a nthetasin(pi/2+theta)cos(pi/2-theta) is -1 b. 1 c. ...

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  13. Prove that: sin^2pi/(18)+sin^2pi/9+sin^2(7pi)/(18)+sin^2(4pi)/9=2

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  14. If A=2sin^2theta-cos2theta, t h e n A lies in the interval (a)[-1,3] ...

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  15. The value of cos^2(pi/6+theta)-sin ^2\ (pi/6-theta) is (a)dot 1/2cos\...

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  16. The value of (cos3theta)/(2cos2theta-1) is equal to (a) costheta (b) ...

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  17. The value of (2(sin2theta+2cos^2theta-1))/(costheta-sintheta-cos3theta...

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  18. 2(1-2sin^2 7theta)sin3theta is equal to a.\ sin 17theta-sin 11theta b....

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  19. cos(36^@-A)cos(36^@+A)+cos(54^@+A)cos(54^@-A)=cos2A

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  20. Prove that: t a nthetatan(60^0-theta)tan(60^0+theta)=tan3thetadot

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