5. Inverse Trigonometric Functions and Basic Trigonometric Equations

Given a right triangle where the length of the adjacent side to angle $x$ is $1$ and the hypotenuse is $2$, in which triangle is the value of $x$ equal to ${cos}^{-1}\left(1,/,2\right)$ (that is, $x=arccos\left(\frac{1}{2}\right)$)?

For which interval of $x$ is the cancellation property ${\sin }^{-1}\left(\sin \right(x\left)\right)=x$ valid?