# How do you use a calculator to approximate arctan15?

Look for the key: ${\tan}^{- 1}$. Press that then enter 15. What happens next depends on the calculator. You need to 'initiate' what you just typed in. I get: $86.1859251 \ldots \ldots$
So for one along you go up $86.1859251 \ldots \ldots$