= √ (sin? 20 -2sin20 cos20 +cos？ 20 )

=√(sin20 -cos20)？

=|sin20 -cos20 |

=cos20 -sin20

Denominator = cos 20-√ (1-cos? 20) (using inductive formula)

=cos20 -√sin？ 20

=cos20 -sin20

So the original formula = (cos 20-sin 20)/(cos 20-sin 20) =1.