Consider \(\triangle ACB\), right-angled at \(C\), in which \(AB = 29 \ \text{units}\), \(BC = 21 \ \text{units}\) and \(\angle ABC = \theta\).
Determine the values of:
(i) \(cos^2 \ \theta + sin^2 \ \theta =\)
(ii) \(cos^2 \ \theta - sin^2 \ \theta =\)