Solve `sin^(-1)(1-x)-2sin^(-1)x=pi/2`

Explanation

`sin^(-1)(1-x)-2sin^(-1)x=pi/2`

Let `x=siny`

`sin^(-1)(1-siny)=2y=pi/2`

`sin^(-1)(1-siny)=(pi/2+2y)`

`1-siny=cos2y`

`1-siny=1-2sin2y`

`2sin^2y=siny`

`siny=0,siny=1/2`

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