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Prove that: 8cos^3pi/9-\ 6cospi/9=1....

Prove that: `8cos^3pi/9-\ 6cospi/9=1.`

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RD SHARMA ENGLISH-TRIGONOMETRIC RATIOS OF MULTIPLE AND SUBMULTIPLE ANGLES-All Questions
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  2. If cos alpha=4/5 and cos beta =5/13, prove that cos (alpha-beta)/2=28/...

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  3. Prove that: 8cos^3pi/9-\ 6cospi/9=1.

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  4. Prove that: 108sinpi/(18)-144sin^3pi/(18)=18

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  5. Prove that cos6A=32cos^6A-48cos^4A+18cos^2A-1

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  6. Prove that : cos Acos(60-A)cos(60+A)=1/4cos3A

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  7. Prove that: "s i n A s i n"(60-"A")sin(60+"A")=1/4sin3"A"dot

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  8. Prove that: "sin"20^0"sin"40^0"sin"60^0"sin"80^0=3/(16)

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  9. prove sin(5theta) = 16sin^5(theta)-20sin^3(theta)+5sin(theta)

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  10. Prove that 4(cos ^(3) 10^(@) + sin ^(3) 20^(@)) = 3 ( cos 10^(@) + sin...

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  11. Prove the following identity: cos^3thetasin3theta+sin^3thetacos3theta=...

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  12. Prove the following identity: \ t a nthetat a n(theta+60^0)+t a ntheta...

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  13. Prove that: t a nA+tan(60^0+A)-t a n(60^0-A)=3t a n3A

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  14. Prove that: cotA+"cot"(60^0+A)-cot(60^0-A)=3cot3A

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  15. Prove the following identity: cot A+cot(60^0+A)+cot(120^0+A)=3cot3A

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  16. Prove that: sin^3A+sin^3((2pi)/3+A)+sin^3((4pi)/3+A)=-3/4sin3Adot

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  17. Prove that: |costhetacos(60^0-theta)cos(60^0+theta)lt=1/4 for all valu...

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  18. Prove that: sin(pi/5) sin2pi/5 sin3pi/5 sin4pi/5=5/16

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  19. Prove that cos((2pi)/(15))cos((4pi)/(15))cos((8pi)/(15))cos((16pi)/(15...

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  20. Prove that: sin 12^0sin 48^0sin 54^0=1/8dot

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