For any real number x satisfying −1≤x≤1, consider the inverse trigonometric expressions arcsinx and arccosx.
(i) State the principal value ranges of arcsinx and arccosx. Explain why these ranges are necessary for defining the inverse functions.
(ii) Prove that arcsinx+arccosx=2π for every x in the interval [−1,1], making explicit reference to the principal value ranges obtained in part (i).