(i) Express tan2θ as the quotient of sin2θ and cos2θ.
(ii) By simplifying the expression obtained in part (i), prove that
tan2θ=1−tan2θ2tanθ.
(iii) State the values of θ (within 0≤θ<π) for which the formula in part (ii) is not defined, giving a brief reason in each case.