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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=........

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A DAS GUPTA-Circular Functions, Identities -Exercise
  1. If sin x + sin y = a, cos x - cos y = b then the value of tan ((y-x)/2...

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  2. The numerical value of sin^(2)5^circ + sin^(2)10^circ + sin^(2)15^circ...

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

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  4. The numerical value of sin pi/18 * sin 5pi/18* sin 7pi/18 is.............

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  5. The numerical value of tan 20^circ* tan 40^circ* tan 80^circ =.

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  6. The numerical value of tan 20^circ* tan 40^circ* tan 80^circ =.

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  7. The numerical value of cos pi/15* cos frac {2pi}{15}* cos frac {4pi}{...

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  8. The numerical value of sin 6^circ* sin 42^circ* sin 66^circ* sin 78^c...

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  9. The numerical value of cos pi/15* cos frac {2pi}{15}* cos frac {4pi}{...

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  10. The numerical value of (where i = sqrt-1) (cos pi/10 + i sin pi/10)(c...

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  11. The numerical value of cot^(2)36^circ* cot^(2)72^circ =.

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  12. The numerical value of sin 12^circ* sin 48^circ* sin 54^circ= .

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  13. If sin 54^circ = 1/2 + sin theta, 0 lt theta lt pi/2, then theta = .

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  14. The numerical value of tan 225^circ *cot 405^circ + tan 765^circ* cot...

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

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  16. If (1 + sin 2x)/(1- sin2x) = tan^(2) *(alpha +x) for all x then the ...

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  17. If cos(x -y), cos x and cos(x + y) are in HP then cos x* sec (y/2)= .

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  18. If A, B, C are in AP and B = pi/4 , then tan A *tan B*tan C = .

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  19. If p in (0, pi) then the set of values of p for which sin p* cos^(3) ...

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  20. sec^(2)theta = frac{4xy}{(x+y)^(2)} is true if and only if

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