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Prove that sum(r=1)^(9) sin^(2) rpi/18 ...

Prove that `sum_(r=1)^(9) sin^(2) rpi/18 =5`.

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A DAS GUPTA-Circular Functions, Identities -Exercise
  1. Find the sum: tan x + 1/2 tan (x/2)+ 1/2^(2) tan (x/2^(2)) +.....+1/2...

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  2. Prove that cosec 2theta = cot theta - cot 2theta . Hence or otherwi...

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  3. Prove that sum(r=1)^(9) sin^(2) rpi/18 =5.

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  4. Find sum(r=1)^(10) cos^(3) rpi/3.

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  5. Sum: sqrt(1 + sin 2alpha) + sqrt(1 + sin 4alpha) + sqrt(1 + sin 6alpha...

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  6. Prove that sin^(2) 12^circ + sin^(2)21^circ + sin^(2)39^circ + sin^(2)...

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  7. If A + B + C = pi, prove that cos A cosec B cosec C + cos B cosec C c...

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  8. Prove that in a triangle ABC, sin^(2)A - sin^(2)B + sin^(2)C = 2sin A...

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  9. Prove that in a triangle ABC, sum (cot B+ cotC)/(tan B + tan C) =1.

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  10. If A + B + C + D = 2pi, prove that: cos A + cos B + cos C + cos D =...

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  11. If alpha + beta- gamma= pi, prove that sin^(2)alpha + sin^(2)beta - s...

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  12. If alpha + beta + gamma = 2 theta, prove that cos theta + cos(theta- ...

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  13. If A + B + C = pi, show that cot A + sinA/(sin B sin C) = cot B + sin...

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  14. If A + B + C = 0, prove that sum sin 2A = 2sum sin A * (1 + sum cos A...

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  15. Prove that tan(x - y) + tan(y - z) + tan(z - x) = tan(x - y) *tan(y -...

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  16. If alpha + beta + gamma + delta = 2pi then prove that sum tan alpha =...

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  17. If x + y + z = xyz, prove that x(1 -y^(2)) (1- z^(2))+ y(1- z^(2))(1- ...

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  18. If x + y + z = xyz, prove that (3x -x^(3))/ (1-3x^(2)) + (3y -y^(3))/(...

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  19. If A + B + C = pi then show that cot theta = cot A + cot B + cot C ⇔ s...

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  20. If theta = pi/7 prove that cos theta* cos 2theta * cos 3theta = 1/8

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