How to put a box around multiple lines. Εμφανές πλαίσιο κουτί σε πολλαπλές γραμμές.

 How to put a box around multiple lines.:



\documentclass{article}
\let\vec\mathbf

$$\begin{document}  \fbox{% \parbox{0.8\linewidth}{% Given the vectors $\vec p$ and $\vec n$ as input, and the function $f$, find the scalar $\lambda$ that minimizes $f(\vec p + \lambda \vec n)$. Replace $\vec p$ by $\vec p + \lambda \vec n$. Replace $\vec n$ by $\lambda \vec n$.% }% } \end{document}$$