Given the inequality:
$$\frac{\pi}{2} > \operatorname{asin}{\left(x \right)}$$
To solve this inequality, we must first solve the corresponding equation:
$$\frac{\pi}{2} = \operatorname{asin}{\left(x \right)}$$
Solve:
$$x_{1} = 1$$
$$x_{1} = 1$$
This roots
$$x_{1} = 1$$
is the points with change the sign of the inequality expression.
First define with the sign to the leftmost point:
$$x_{0} < x_{1}$$
For example, let's take the point
$$x_{0} = x_{1} - \frac{1}{10}$$
=
$$- \frac{1}{10} + 1$$
=
$$\frac{9}{10}$$
substitute to the expression
$$\frac{\pi}{2} > \operatorname{asin}{\left(x \right)}$$
$$\frac{\pi}{2} > \operatorname{asin}{\left(\frac{9}{10} \right)}$$
pi
-- > asin(9/10)
2
the solution of our inequality is:
$$x < 1$$
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