(a) Let $\sin{x = \mathcal{z\ \Rightarrow}d\ (\sin{x) = d\mathcal{z}}}$ $\therefore\ \int_{}^{}{\frac{d\mathcal{z}}{\sqrt{1 - \mathcal{z}^{2}}} = \sin^{- 1}{\mathcal{z +}c}}$ $= \sin^{- 1}{(\sin{x) + c = x + c}}$
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Ph.D. in Physics with 19+ years of teaching experience.