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Prove that: cos 20^0cos 100^0+cos 100^0c...

Prove that: `cos 20^0cos 100^0+cos 100^0cos 140^0-\ cos 140^0cos 200^0=-3/4`

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RD SHARMA ENGLISH-TRANSFORMATION FORMULAE-All Questions
  1. Prove that: \ cos A+cos3A+cos5A+cos7A=4cos A cos2A cos4A

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  2. Prove that sinA+sin2A+sin4A+sin5A=4 cos(A/2)cos((3A)/2)sin3A

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  3. Prove that: cos 20^0cos 100^0+cos 100^0cos 140^0-\ cos 140^0cos 200^0=...

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  4. Prove that: \ sin3A+sin2A-sin A=4sin A cos (A/2)cos((3A)/2)

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  5. Prove that:costhetacos(theta/2)-cos3thetacos((9theta)/2)=sin((7theta)/...

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  6. Prove that: (sin A+sin3A)/(cos A-cos3A)=cotA

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  7. Prove that: (sin9A-sin7A)/(cos7A-cos9A)=cot8A

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  8. Prove that: (sin A-sin B)/(cos A+cos B)=tan((A-B)/2)

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  9. Prove that: (sin A+sin B)/(sin A-sin B)=tan((A+B)/2)cot((A-B)/2)

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  10. Prove that: (cos A+cos B)/(cos B-cos A)=cot((A+B)/2)cot((A-B)/2)

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  11. Prove that:(sinA+sin3A+sin5A)/(cos A+cos3A+cos5A)=tan3A

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  12. Prove that: (cos3A+2cos5A+cos7A)/(cos A+2cos3A+cos5A)=(cos5A)/(cos3A)

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  13. Prove that: (cos4A+cos3A+cos2A)/(sin4A+sin3A+sin2A)=cot3A

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  14. Prove that: (sin3A+sin5A +sin7A+sin9A)/(cos3A+cos5A+cos7A+cos9A)=tan6A

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  15. Prove that: (sin5A cos2A-sin6A\ cos A)/(sin A\ sin2A-cos2A cos3A)=t a ...

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  16. Prove that: (sin3A cos4A-sin Acos2A)/(sin4A sin A+cos6A cos A)=tan2A

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  17. Prove that: (sin11 A\ sin A+sin7A\ sin3A)/(cos 11\ A\ sin A+cos7Asin3A...

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  18. Prove that: (sinA+sin3A+sin5A+sin7A)/(cosA+cos3A+cos5A+cos7A)=tan4A

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  19. prove that : (sinA+2sin3A+sin5A)/(sin3A+2sin5A+sin7A)=(sin3A)/(sin5A)

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  20. Prove that: (sin(theta+varphi)-2sintheta+"sin"(theta-varphi))/(cos(the...

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