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Prove that 4cos((2pi)/7).cos(pi/7)-1=2co...

Prove that `4cos((2pi)/7).cos(pi/7)-1=2cos((2pi)/7)`.

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ALLEN-BASIC MATHS,LOGARITHIM, TRIGNOMETRIC RATIO AND IDENTITIES AND TRIGNOMETRIC EQUATION -EXERCISE (S-1)
  1. If the value of the expression sin 25^@* sin 35^@* sin 85^@ can be exp...

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  2. Prove that (4cos^2 9^0-3)(4cos^2 27^0-3)=tan9^0dot

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  3. Prove that 4cos((2pi)/7).cos(pi/7)-1=2cos((2pi)/7).

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  4. Let P(k)=(1+cospi/(4k)) (1+cos((2k-1)pi)/(4k)) (1+cos((2k+1)pi)/(4k))...

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  10. If a leq 3 cos (theta+pi/3)+5cos theta+3 leq b, find a and b, where ...

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  11. Let k=1^@ then prove that sum(n=0)^(88)1/(cosnkcos(n+1)k)=cosk/sin^2k

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