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cos. (pi)/(13) + cos. (5pi)/(13) + cos. ...

`cos. (pi)/(13) + cos. (5pi)/(13) + cos. (8pi)/(13) + cos. (12pi)/(13)=`

A

0

B

1

C

-1

D

2

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AAKASH SERIES-TRIGONOMERTIC RATIOS-PRACTICE EXERCISE
  1. cos 20^(@) + cos 40^(@) + cos 60^(@) +...+cos160^(@)+cos 180^(@)=

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  2. cos5^(@) + cos 24^(@) + cos 175^(@) + cos 204^(@) + cos 300^(@) =

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  3. cos. (pi)/(13) + cos. (5pi)/(13) + cos. (8pi)/(13) + cos. (12pi)/(13)=

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  4. cos. (3pi)/(19) + cos . (7pi)/(19) + cos. (12pi)/(19) + cos. (16pi)/(1...

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  5. tan. (pi)/(10) + tan. (3pi)/(10) + tan. (7pi)/(10) + tan. (9pi)/(10) ...

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  6. If alpha , beta are supplementary angles , then cos^(2)alpha + sin^(...

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  7. If ABCD is a quadrilateral then Sec^(2) ((A+B)/(4))- Cot^(2) ((C+D)/(...

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  8. If ABCD is a cyclic quadrilateral then co (180^(@) +A) + cos (180^(@)...

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  9. If alpha , beta are complementary angles , sin alpha = 3//5 , then s...

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  10. Prove that sin^(2)5^(@) +sin^(2)10^(@) + sin^(2)15^(@)+...+sin^(2)90^(...

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  11. cos^(2)5^(@)+cos^(2)10^(@)+cos^(2)15^(@)+.....+cos^(2) 90^(@)=

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  12. cos^(@)cos2^(@)cos3^(@).......cos179^(@)=

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  13. tan10^(@) tan 20^(@) tan 30^(@) tan 40^(@) tan 50^(@) tan 60^(@) tan 7...

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  14. [(Tan ( pi - x) Tan (1.5 pi + x))/(Cos^(2)(x-1.5pi))-(Cos(1.5pi + x))/...

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  15. If cos A = 3/4 then (2cos A + 3 sin A)/(4 cos A - sin A) =

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  16. If theta is acute and (1-a^(2)) sin theta =(1+ a^(2)) cos theta , t...

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  17. If cot theta=-3//4 and theta is not in the second quadrant , then ...

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  18. If tan 20^(@) = lambda , " then " (tan 250^@ + tan 340^(@))/(tan 200^...

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  19. 3(sin x + cos x )^(4) + 6(sin x - cos x )^(2) + 4(sin^(6) x + cos^(6) ...

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  20. If k=( sec A + tan A) ( sec B+ tan B) sec C + tan C)=(sec A - tan A)(s...

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