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If cos alpha+cos beta=0=sin alpha+sinbet...

If `cos alpha+cos beta=0=sin alpha+sinbeta, then cos2alpha+cos 2beta=`

A

`-2sin(alpha+beta)`

B

`-2cos (alpha+beta)`

C

`2sin(alpha+beta)`

D

`2cos (alpha+beta)`

Text Solution

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The correct Answer is:
B
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OBJECTIVE RD SHARMA-TRIGONOMETRIC RATIOS AND IDENTITIES-Chapter Test
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  9. If cosectheta=(p+q)/(p-q),then cot(pi,//4+theta//2)=

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  10. If sinalpha+sin beta=a and cos alpha+cos beta=b,then sin(alpha+beta)=

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  11. If cos(alpha+beta)=4/5, sin(alpha-beta)=5/13and alpha, beta between 0 ...

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  12. The vlaue of cos^(2)76^(@)+cos^(2)16-cos76^(@)cos16^(@),is

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  14. If (a^(2)+1)/(2a)=costheta, then (a^(6)+1)/(2a^(3))=

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  16. If tan alpha=(1+2^(-x))^(-1), tan beta=(1+2^(x+1))^(-1) then alpha+bet...

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  17. A and B are positive acute angles satisfying the equations 3cos^(2)A...

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  20. Let thetain(0,pi//4)and t(1)=(tantheta)^(tantheta), t(2)=(tantheta)^(...

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