Answer
$0$
Work Step by Step
The identity says: $1+\tan^2{(\theta)}=\sec^2{(\theta)}$.
We also know that $\sec{(\theta)}=\csc{(90^{o}-\theta)}$, hence $1+\tan^2{(5^{o})}-\csc^2{(85^{o})}=\sec^2{(5^{o})}-\csc^2{(85^{o})}=\csc^2{(85^{o})}-\csc^2{(85^{o})}=0.$
