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Prove the following : sin 51^@ + cos 8...

Prove the following :
`sin 51^@ + cos 81^@ = cos 21^@`.

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MODERN PUBLICATION-TRIGNOMETRY-EXERCISE
  1. Prove the following : 4 sin A sin (60^@ + A) sin (60^@ - A) = sin 3A...

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  2. Prove the following : sin 10^@ + sin 20^@ + sin 40^@ + sin 50^@ = si...

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  3. Prove the following : sin 51^@ + cos 81^@ = cos 21^@.

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  4. Prove the following : sin 10^@ sin 50^@ sin 70^@ = 1/8.

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  5. Prove the following : sin 10^@ sin 30^@ sin 50^@ sin 70^@ = 1/16.

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  6. Prove the following : sin 20^@ sin 40^@ sin 60^@ sin 80^@ = 3/16.

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  7. Prove the following : cos 10^@ cos 50^@ cos 70^@ = sqrt3/8.

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  8. Prove the following : cos 10^@ cos 30^@ cos 50^@ cos 70^@ = 3/16.

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  9. Prove the following : cos 20^@ cos 40^@ cos 80^@ =1/8.

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  10. Prove the following : cos 20^@ cos 40^@ cos 60^@ cos 80^@ =1/16.

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  11. Prove the following : cos 10^@ cos 30^@ cos 50^@ cos 70^@ = 3/16.

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  12. Prove the following : tan 20^@ tan 40^@ tan 60^@ tan 80^@=3.

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  13. Prove the following : tan 20^@ tan 40^@ tan 80^@= tan 60^@.

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  14. Prove that: 2cos frac (pi)(13)cos frac (9pi)(13)+cos frac (3pi)(13)+co...

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  16. Prove the following : cot 4 theta(sin 5 theta+ sin 3 theta)=cot thet...

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  17. Prove the following : cos 3 theta+ cos 5 theta+ cos 7 theta+ cos 9 t...

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  18. Prove the following: sin2 x + 2 sin 4x + sin 6x = 4 cos^2 x sin 4x

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  19. Prove the following : sin theta+ sin 3 theta+ sin 5 theta+sin 7 thet...

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  20. Prove the following : cos 7 theta + cos 5 theta + cos 3 theta +cos t...

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