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The value of underset(r=1)overset9sum si...

The value of `underset(r=1)overset9sum sin^2(rpi)/18`=

A

2

B

3

C

4

D

5

Text Solution

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The correct Answer is:
D
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PATHFINDER-TRIGONOMETRIC RATIOS AND IDENTITIES-QUESTION BANK
  1. Find the value of (1+cos (pi/8))(1+cos(3pi/8))(1+cos(5pi/8))(1+cos(7pi...

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  2. (cos^4(pi/8))+(cos^4((3pi)/8))+(cos^4((5pi)/8))+(cos^4((7pi)/8)) is

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  3. The value of underset(r=1)overset9sum sin^2(rpi)/18=

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  4. If A+B+C=(3pi)/2, then cos2A +cos2B+cos2C is

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  5. The number of points of intersection of 2y=1 and y=sinx, -2pilexle2pi

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  6. If sinalpha, sinbeta and cosalpha are in G.P. then roots of the equati...

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  7. If x=secphi-tanphi and y=cosecphi+cotphi, then

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  8. For any triangle ABC, ((a+b+c)(b+c-a)(c+a-b)(a+b-c))/(4b^2c^2)is equa...

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  9. Which one is correct?

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  10. In a DeltaABC, if cotAcotBcotCgt0, then the Delta is

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  11. cos(pi/14) + cos ((3pi)/14) + cos((5pi)/14)=

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  12. If (2sinalpha)/(1+cosalpha+sinalpha)=x, then (1-cosalpha+sinalpha)/(1+...

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  13. If secalpha and cosecalpha are two roots of x^2-px+q=0 then

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  14. If costheta + sectheta = (-2) then cos^ntheta + sec^ntheta= (If n is e...

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  15. Given A=sin^2theta +cos^4theta. Then for all real values of theta, whi...

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  16. The minimum value of cos(cosx) is

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  17. If S=cos^2(pi/n) + cos^2((2pi)/n) +....+ cos^2((n-1)pi)/n, then S equa...

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  18. If cos5theta = acostheta +bcos^2theta + c.cos^5theta =d, then

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  19. prove that In an acute angled triangle ABC, secA+ secB+secCge6 is

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  20. If Tn=sin^ntheta+ cos^ntheta, then (T6-T4)/T6=m holds for value of m s...

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