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The value of sin 78^0-sin 66^0-sin 42^0+...

The value of `sin 78^0-sin 66^0-sin 42^0+sin6^0` is a. `-1` b. `1//2` c. `-1//2` d. none of these

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ALLEN-TRIGONOMETRIC RATIOS AND IDENTITIES-All Questions
  1. Prove that :t a n A+tan(60^0+A)+tan(120^0+A)=3t a n3A

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  2. sin (67(1)/2)^(@)+cos(67(1)/2)^(@) is equal to

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  3. The value of sin 78^0-sin 66^0-sin 42^0+sin6^0 is a. -1 b. 1//2 c. -1/...

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  4. In any triangle A B C ,\ sin A-cos B=cos C ,\ the angle\ B is a.pi...

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  5. If A+B+C=(3pi)/2, t h e ncos2A+cos2B+cos2C is equal to 1-4cos Acos Bc...

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  6. Prove that 5 cos theta+3cos(theta+(pi)/(3))+3 lies between -4 and 10.

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  7. Find the maximum value of 1+sin((pi)/(4)+theta) +2sin ((pi)/(4)-thet...

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  8. Prove that t a n A+2t a n2A+4t a n4A+8cot8A=cot Adot

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  9. sum(r=1)^(n-1)cos^(2) (rpi)/2 is equal to

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  10. Prove that: (1+sec2theta)(1+sec4theta)(1+sec8theta)(1+sec2^ntheta)=t a...

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  11. Prove that tan alpha+2 tan 2 alpha+2^(2)tan2^(2)alpha+.................

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  12. S=cosecx+cosec 2x+cosec 4x+…+cosec 2nx=cot(x/2)−cot2nx

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  13. The expression (tan(x-(pi)/(2)).cos((3pi)/(2)+x)-sin^(3)((7pi)/(2)-x...

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  14. The values of cos^2 73^0+cos^2 47^0-sin^2 43^0+sin^2 107^0 is equal t...

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  15. The expression (sin 22^0cos8^0+cos 158^0cos98^0)/(sin 23^0cos7^0+cos 1...

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  16. The two legs of a right triangle are sin theta+sin((3pi)/(2)-theta) an...

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  17. If tantheta=sqrt(a/b)where a , b are positive reals then the value o...

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  18. The expression (sin(alpha+theta)-"sin"(alpha-theta))/(cos(beta-theta)-...

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  19. Exact value of cos 20^0+2sin^2\ \ 55^0-sqrt(2)sin65^0\ is- a.1 b. 1/(...

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  20. If cos(theta+phi)=mcos(theta-phi) ,then tantheta is equal to a.((1+m)...

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