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If cos(x-y), cosx and cos(x+y) are in H....

If `cos(x-y), cosx and cos(x+y)` are in H.P., then `cos x sec (y/2)` equals

A

1

B

2

C

`sqrt2`

D

none of these

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The correct Answer is:
C
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OBJECTIVE RD SHARMA-TRIGONOMETRIC RATIOS AND IDENTITIES-Exercise
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  3. If cos(x-y), cosx and cos(x+y) are in H.P., then cos x sec (y/2) equal...

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  4. The value of tan20^(@)+2 tan50^(@)-tan70^(@), is

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  6. Minimum value of cos2theta+costheta for all real value of theta is

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  7. cos9^@-sin9^@=

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  8. If y=(sin 3theta)/(sintheta), theta nen pi, then

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  9. If tan(picostheta)=cot(pisintheta),0lt thetalt(3pi)/(4), then sin(thet...

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  10. If tan(picostheta)=cot(pisintheta),"then the value of"sin(theta+(pi)/(...

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  13. If alpha and beta be between 0 and (pi)/(2)and if cos(alpha+beta)=(12)...

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  14. If tan (alpha/2) and tan beta/2are the roots of the equation 8x^2-26x+...

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  15. 2x^(2) + 3x - alpha - 0 " has roots "-2 and beta " while the equation ...

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  16. If A+B+C=0, then the value of sum cot (B+C-A) cot (C+A-B) is equal to

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  18. For -(pi)/(2)lttheta(pi)/(2),(sintheta+sin2theta)/(1+costheta+cos2thet...

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