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Let x1=prod(r=1)^5cos(rpi)/(11)\ a n d\ ...

Let `x_1=prod_(r=1)^5cos(rpi)/(11)\ a n d\ x_2=sum_(r=1)^2cos(rpi)/(11),` then show that `x_1dotx_2=1/(64)(cos e c\ pi/(22)),\ w h e r e\ prod\ ` denotes the continued product.

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