For the three standard trigonometric functions y=sinx, y=cosx and y=tanx, respond to the following items.
(i) Define the period of a real-valued function. Hence state the fundamental period of each of the three functions mentioned above.
(ii) Explain, with reason, why the ranges of sinx and cosx are identical while the range of tanx is different.
(iii) Describe the complete domain of tanx, making clear reference to the points where the function is not defined.