Source TeX:

\begin{array}{rll}\tan\left(\text{arcsec}(4)\right)&=\tan(\theta)&\small\text{; car }\theta=\text{arcsec}(4)\\&=\dfrac{\sqrt{15}}{1}&\small\text{; car }\tan(\theta)=\frac{\text{opp}}{\text{adj}}\\[1em]&=\sqrt{15}&\end{array}