William Anthony Granville, Elements of the Differential and Integral Calculus… (1911)
“ XXIV ∴ . ↑ Graph of arc sin vIt should be remembered that this function is defined only for values of between -1 and +1 inclusive and that (the function) is many-valued, there being infinitely many arcs whose sines will equal . Thus, in the figure (the locus of ) , when .In the above discussion, in order to make the function single-valued; only values of between and inclusive (points on arc ) are considered; that is, the arc of smallest numerical value whose sine is . ↑ Graph of arc cos vThis function is defined only for values of between -1 and +1 inclusive, and is many-valued. ”
