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If A+ B+C= 180^(@) " then " cos 2A+ cos ...

If `A+ B+C= 180^(@) " then " cos 2A+ cos 2B + cos 2C+ 1=`

A

`1+ 4 sin A sin B sin C `

B

`1-2 sin A sin B sin C `

C

`2+2 sin A sin B sin C `

D

`4 sin A sin B cos C `

Text Solution

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The correct Answer is:
A
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DIPTI PUBLICATION ( AP EAMET)-TRIGONOMETRIC RATIOS AND IDENTITIES -EXERCISE 1 E ( TRIGONOMETRIC IDENTITIES )
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  2. If A+B+C= 90^(@) " then " sin 2A+ sin 2B- sin 2C=

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  3. If A+ B+C= 180^(@) " then " cos 2A+ cos 2B + cos 2C+ 1=

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  4. If A+B+C=(pi)/(2), then prove that sin ^(2) A+ sin ^(2) B + sin ^(2) C...

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  5. If A+B+C=90^(@) " then " cos^(2) A + cos^(2) B + cos^(2) C =

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  6. If A+B+C=90^(@) " then " ( cos 2A + cos 2 B+ cos 2C-1)/( sin A sin B s...

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  7. If A+B+C=0, then prove that sin 2A + sin 2B+ sin 2C=-4sin A sin B sin ...

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  8. If A+B+C=0^@ " then " sin A + sin B + sin C =

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  9. A + B+ C =0అయితే , cos^(2) A + cos^(2) B +cos^(2)C = 1+2 cos A cos B c...

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  10. A + B+ C =0అయితే , cos^(2) A + cos^(2) B +cos^(2)C = 1+2 cos A cos B c...

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  11. If A+B+C=(3pi)/(2), prove that cos 2A+ cos 2B+ cos 2C=1-4 sin A sin B ...

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  12. If A+B +C = 270^@, then cos 2A + cos 2B +cos 2C +4sin A sin B sin C=

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  13. If A+B+C=90^(@) then cos^(2)A+cos^(2)B+cos^(2)C=

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  14. If A+B+C = 2S, then prove that sin(S-A)+sin(S-B)+sinC = 4 cos ((S-A)...

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  15. If A+B+C= 2S , " then " sin (S-A) sin(S-B) + sinS sin(S-C)=

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  19. If alpha + beta + gamma = 2 theta , " then " cos theta + cos ( theta...

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  20. If A+B+C+D=180^(@) " then " cos A cos B+ cos C cos D =

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