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If z=costheta+isintheta is a root of the...

If `z=costheta+isintheta` is a root of the equation `a_0z^n+a_2z^(n-2)++a_(n-1)z^+a_n=0,` then prove that `a_0+a_1costheta+a_2^cos2theta++a_ncosntheta=0` `a_1"sin"theta+a_2^sin2theta++a_nsinntheta=0`

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