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4( cos^(3) 10^(@) + sin^(3) 20^(@))=...

`4( cos^(3) 10^(@) + sin^(3) 20^(@))= `

A

`3(cos 20^(@) + cos 40^(@))`

B

`3 ( cos 10^(@) + sin 20^(@))`

C

` 3( cos 20^(@) + sin 40^(@))`

D

`3( cos 10^(@) + cos 20^(@)) `

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The correct Answer is:
B
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DIPTI PUBLICATION ( AP EAMET)-TRIGONOMETRIC RATIOS AND IDENTITIES -EXERCISE 1 C ( MULTIPLE AND SUBMULTIPLE ANGLES )
  1. 8 cos^(3) 20^(@) -6 cos 20^(@) =

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  2. 4(cos^3 20^(@) + cos^(3) 40^(@))=

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  3. 4( cos^(3) 10^(@) + sin^(3) 20^(@))=

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  4. if ( cos ^(3) 20^@ + cos^(3) 40^(@))/( cos 20^@+ cos 40^(@)) = k ,the...

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  5. cos theta cos (60^(@) + theta ) * cos (60^(@) - theta ) =

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  6. sin^(2) theta + sin^(2)(60^@ + theta ) + sin^(2)(60^(@) - theta ) =

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  7. cos^(2) A + cos^(2) ( 120^(@) + A)+ cos^(2) (120^(@) - A )=

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  8. cos^(3) theta + cos^(3) ( 120^(@) +theta ) + cos^(3) (120^(@) - theta ...

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  9. sin^(2) 20^(@) + sin^(2) 100^@ + sin^(2) 140^(@) =

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  10. cos^(3) 20^(@) + cos^(3) 100^(@) + cos^(3) 140^(@) =

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  11. cos^(2)(theta-45^(@))+cos^(2)(theta+15^(@)-cos^(2)(theta-15^(@))=

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  12. If 4 sin(60^(@) + theta ) sin (60^(@) - theta )-1=k cos 2 theta , th...

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  17. If sin 18^(@)=(sqrt(5)-1)/(4) , then sin 81^(@)=

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  18. Prove that (1)/(cos 290^(@))+(1)/(sqrt3 sin 250^(@) )=(4)/(sqrt3)

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  19. Show that 1/(sin 10^(@)) - (sqrt(3))/(cos 10^(@)) = 4.

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  20. Prove that sqrt3 csc 20 ^(@)- sec 20^(@)=4

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