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

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

A

`1- 4 cos A cos B cos C`

B

`4 sin A sin B sin C`

C

`1-2 cos A cos B cos C`

D

`1-4 sin A sin B sin C`

Text Solution

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The correct Answer is:
D
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ML KHANNA-TRIGONOMETRY RATIOS AND IDENTITIES-PROBLEM SET (6) ( MULTIPLE CHOICE QUESTIONS)
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  2. If A+B+C=pi, then cos2A+cos2B+cos2C=

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

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  4. If A +B = ( pi )/( 3) and cos A + cos B =1, then which of the followin...

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  6. If A+B+C=pi, prove that : (sin 2A+sin 2B + sin 2C)/(sinA+sinB+sinC) = ...

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  7. (sin 2A+sin 2B + sin 2C)/(cos A + cos B + cos C-1) = 8 cos, A/2 cos, B...

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  8. if A+B+C=pi then sin^(2) A + sin^(2) B - sin^(2) C =

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  10. If A+B+C=180^(@), then prove that cos^(2)(A)/(2)+cos^(2)(B)/(2)+cos^(2...

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  12. If alpha+beta+gamma=2pi, prove that : cos^2 alpha + cos^2 beta + cos^2...

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  14. If A,B,C are the angles of a triangle, then sin^(2) A + sin^(2) B + si...

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  15. cos^(2) A + cos^(2) B + cos^(2) C =

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  16. sin^(2) A + sin ^(2) B +sin^(2) C =

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  17. If A+B+C=pi , prove that : sin^2, A/2 + sin^2, B/2 -sin^2, C/2 =1-2 co...

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  18. If : cos^(2) A + cos^(2) B + cos^(2) C = 1, "then" : Delta ABC is

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  19. In a !ABC if sin A cos B = 1/4 and 3 tan A = B , then the triangle is

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