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Prove that 2cos(pi/13)cos((9pi)/13)+cos(...

Prove that `2cos(pi/13)cos((9pi)/13)+cos((3pi)/13)+cos((5pi)/13)=0`

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V PUBLICATION-TRIGNOMETRC FUNCTIONS-QUESTION BANK
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  3. Prove that 2cos(pi/13)cos((9pi)/13)+cos((3pi)/13)+cos((5pi)/13)=0

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  11. Find sin(x/2) , cos(x/2) and tan(x/2) if cosx=(-1/3) and x lies in the...

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