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If tanalpha=(1)/(7)andtanbeta=(1)/(3), ...

If `tanalpha=(1)/(7)andtanbeta=(1)/(3)`, then `cos2alpha` is equal to

A

`sin2beta`

B

`sin4beta`

C

`sin3beta`

D

`cos2beta`

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The correct Answer is:
B
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KUMAR PRAKASHAN-TRIGONOMETRIC FUNCTIONS -SOLUTION OF NCERT EXEMPLAR PROBLEMS (OBJECTIVE TYPE QUESTIONS)
  1. If tanalpha=(m)/(m+1)andtanbeta=(1)/(2m+1) then (alpha+beta) is equal ...

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  2. The minimum value of 3cosx+4sinx+8 is

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  3. The value of tan3A-tan2A-tanA is

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  4. The value of sin(45^(@)+theta)-cos(45^(@)-theta) is

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  5. The value of cot((pi)/(4)+theta)cot((pi)/(4)-theta) is

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  6. cos2thetacos2phi+sin^(2)(theta-phi)-sin^(2)(theta+phi) is equal to

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  7. The value of cos12^(@)+cos84^(@)+cos156^(@)+cos132^(@) is

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  8. If tanA=(1)/(2)andtanB=(1)/(3), then tan(2A+B) is equal to

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  9. The value of sin""(pi)/(10)sin""(13pi)/(10) is

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  10. The value of sin50^(@)-sin70^(@)+sin10^(@) is

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  11. If sintheta+costheta=1, then the value of sin(2theta) is

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  12. If alpha+beta=(pi)/(4), then the value of (1+tanalpha)(1+tanbeta) is

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  13. If sintheta=(-4)/(5)andtheta lies in third quadrant, then the value of...

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  14. The number of solutions of equation tanx+secx=2cosx lying in the inter...

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  15. The value of sin((pi)/(18))+sin((pi)/(9))+sin((2pi)/(9))+sin((5pi)/(18...

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  16. If A lies in the second quadrant and 3tanA+4=0, then the value of 2cot...

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  17. The value of cos^(2)48^(@)-sin^(2)12^(@) is

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  18. If tanalpha=(1)/(7)andtanbeta=(1)/(3), then cos2alpha is equal to

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  19. If tantheta=(a)/(b), then bcos2theta+asin2theta is equal to

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  20. If for real values of x, costheta=x+(1)/(x), then

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