nested radical

[Sonal7]

That line is one step of the answer to this Q. Its got transposed to the wrong Question's answer. I feel like swearing but its fine. My fault for not following through my answers to the end and checking.

 

[Sonal7]

Can you square what is inside the parenthesis? Then subtract it from 1?

Thank you so much for your help.

 

[Sonal7]

I don't get there either. I get \(\displaystyle \frac{\sqrt{3}}{2}\)

Thanks.