solve `sin^(-1) x le cos^(-1) x`

Explanation

`cos^(-1) x ge sin^(-1) x`
or `(pi)/(2) - sin^(-1) x ge sin^(-1) x`
`(pi)/(2) ge 2 sin^(-1) x`
`(-pi)/(2) le sin^(-1) x le (pi)/(4)`
or `-1 le x le sin ((pi)/(4))`
`rArr x in [-1, (1)/(sqrt2)]`