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Prove that sin. (2pi)/(7)+sin.(4pi)/(7)+...

Prove that `sin. (2pi)/(7)+sin.(4pi)/(7)+sin. (8pi)/(7)=(sqrt(7))/(2)`.

A

`sqrt7//8`

B

`1//8`

C

`sqrt7//2`

D

`-sqrt7//2`

Text Solution

Verified by Experts

The correct Answer is:
C
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OBJECTIVE RD SHARMA ENGLISH-TRIGONOMETRIC RATIOS AND IDENTITIES-Exercise
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  2. The value of sin""(pi)/(7)+sin""(2pi)/(7)+sin""(3pi)/(7), is

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  3. Prove that sin. (2pi)/(7)+sin.(4pi)/(7)+sin. (8pi)/(7)=(sqrt(7))/(2).

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  4. cos""(2pi)/(15)cos""(4pi)/(15)cos""(8pi)/(15)cos""(16pi)/(15)=(1)/(16)

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  6. If cosA+cosB=m and sinA+sinB=n then sin(A+B)=

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  11. For x in R, tanx+1/2tan""(x)/(2)+1/((2^2))tan""(x)/(2^(2))+...+(1)/(...

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