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Prove that cos 6^(@) cos 42^(@) cos 60...

Prove that
`cos 6^(@) cos 42^(@) cos 60^(@) cos 78^(@)=1/16` .

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MODERN PUBLICATION-TRIGNOMETRY-EXERCISE
  1. Prove that : sin 12^@ sin48^@ sin 54^@=1/8.

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  2. Prove that : sin 6^@ sin 42^@ sin 66^@ sin 78^@ =1/16.

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  3. Prove that cos 6^(@) cos 42^(@) cos 60^(@) cos 78^(@)=1/16 .

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  4. Prove that : 16 cos frac (2pi)(15) cos frac (4pi)(15) cos frac (8pi)(1...

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  5. Prove that : (1+cos frac (pi)(8)) (1+cos frac (3pi)(8)) (1+cos frac ...

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  6. If A+B+C=pi , then, find sin 2A+ sin 2B+ sin 2C.

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  7. If A+B+C=pi , then, find sin 2A+ sin 2B+ sin 2C.

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  8. If A + B + C =pi, prove that : cos 2A + cos 2B -cos 2C= 1-4sin A sin B...

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  9. If A + B + C =pi, prove that : cos 2A - cos 2B + cos 2C= 1-4 sin A co...

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  10. If A + B + C =pi, prove that : cos 2A - cos 2B- cos 2C= -1+4 cos A si...

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  11. If A + B + C =pi, prove that : . sin A + sin B+sinC = 4 cos frac (A)(2...

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  12. If A + B + C =pi, prove that : cos A - cos B + cos C= -1+4 cos frac (...

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  13. If A + B + C =pi, prove that : cos A+cos B - cos C= 4 cos frac (A)(2)...

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  14. If A + B + C =pi, prove that : cos A+cos B+cos C=1+ 4 sin frac (A)(2) ...

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  15. If A + B + C =pi, prove that : cos A + cos B - cos C> 1.

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  16. If A + B + C =pi, prove that : (sin A + sin B +sin C)/(sin A + sin B -...

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  17. If A + B + C =pi, prove that : (sin 2A + sin 2B + sin 2C)/(sin A + si...

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  18. If A + B + C =pi, prove that : (sin 2A + sin 2B + sin 2C)/(cos A + cos...

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  19. If A+B+C=180^(@), then find the value of (cos A)/(sin B sin C)+(cosB)/...

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  20. If A+B+C=pi , then, find sin 2A+ sin 2B+ sin 2C.

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