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If A+B+C=(3pi)/2, then cos2A +cos2B+cos2...

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

A

1-4 cosA cosB cosC

B

4 sinA sinB sinC

C

1+2 cosA cosB cosC

D

1-4 sin A sin B sin C

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The correct Answer is:
D
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PATHFINDER-TRIGONOMETRIC RATIOS AND IDENTITIES-QUESTION BANK
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  6. If x=secphi-tanphi and y=cosecphi+cotphi, then

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  7. 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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  8. Which one is correct?

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

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

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

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

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

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

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  15. The minimum value of cos(cosx) is

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

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

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

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

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