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Prove that cos(120^@-A)+cosA+cos(120^@+A...

Prove that `cos(120^@-A)+cosA+cos(120^@+A)=0`.

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MAHAVEER PUBLICATION-TRIGONOMETRIC RATIOS-QUESTION BANK
  1. Prove that cosec^2theta+sec^2theta=(sec^2theta)/(sin^2theta)

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  2. (1+sin2theta+cos2theta)/(1+sin2theta-cos2theta)=

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  3. Prove that cos(120^@-A)+cosA+cos(120^@+A)=0.

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  4. Prove that tan(45^@-theta)=(cos theta-sin theta)/(cos theta + sin thet...

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  5. Prove that tan(pi/4+theta/2)=sec theta+tan theta

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  6. sin 20^(@) sin 40^(@) sin 60^(@) sin 80^(@) =(3)/(16)

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  7. If A+B+C=pi, prove that sin 2A+sin 2B-sin 2C=4 cos A cos B sin C

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  8. If A+B+C=pi, prove that tan A+tan B+tan C= tanA tan B tan C

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  9. If A+B+C=pi/2, prove that tan A tan B+tan B tan C+tan C tan A=1

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  10. If A+B+C=pi, prove that: "sin" A+"sin" B-"sin" C=4 "sin"(A)/(2)"sin...

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  11. If A+B+C=pi and cos A=cos B. cosC,prove that cot B cot C=1/2

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  12. Express sin 6theta+sin3theta as a product.

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  13. Evaluate using multiple angle formula: sin15^@

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  14. Evaluate using multiple angle formula: cos15^@

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  15. Evaluate using multiple angle formula: tan15^@

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  16. Prove that :(tan69^0+t a n 66^0)/(1-t a n 69^0t a n\ 66^0)=-1

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  17. Prove that: (cos 11^0+"sin"11^0)/(cos 11^0-"sin"11^0)=t a n 56^0

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  18. Prove that (cos 8^(@) - sin 8^(@))/(cos 8^(@) + sin 8^(@)) = tan 3...

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  19. Prove that: cos 80^0+cos 40^0-cos 20^0=0

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  20. Prove that:cos420^@ sin390^@+ sin(-300^@)cos(-330^@)=1

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