Adding a title to theorem environment

Question

I am trying to use the theorem environment in my work as Sample Problem.

This is my MWE:

\documentclass{book}

\usepackage{amsthm}

\newtheoremstyle{mythmstyle}
    {}{}{}{}
    {\bf}
    {}
    {\newline}
    {}
\theoremstyle{mythmstyle}
\newtheorem{mythm}{Sample Problem}[chapter]
\setcounter{chapter}{2}

\begin{document}
\chapter{New Chapter}
\begin{mythm}
    Problem statement goes here. But, where does go title?
\end{mythm}
\end{document}

And the output,

Actually, I need something like this,

In other words, my Sample Problem lacks a Title.

How can I include a title within the theorem environment?

Answer 1

Here's a solution with thmtools, which eases defining new theorem styles:

\documentclass{book}
\usepackage[utf8]{inputenc} \usepackage{fourier, erewhon, cabin}
\usepackage[table, x11names]{xcolor} \usepackage{mathtools}
\usepackage{amsthm, thmtools}
\usepackage{microtype} \SetTracking[no ligatures = {f}]{encoding = *}{50}
\declaretheoremstyle[%
headfont=\color{SteelBlue3}\sffamily\bfseries\lsstyle,
within=chapter, headpunct={\medskip}, postheadspace=\newline, notefont=\color{black}\mdseries, notebraces = {\quad}{},spaceabove = 8pt,spacebelow = 8pt]%
{sample}

\declaretheorem[name=Sample Problem, style=sample]{mypb}

\begin{document}

\setcounter{chapter}{3}

\begin{mypb}[Adding vectors in a drawing, orienteering]
  Show the following assertion is true: %
  \begin{equation*}
    a = a
  \end{equation*}
\end{mypb}

\end{document}

Answer 2

The title goes in squared brackets at the beginning of the theorem.

\begin{mythm}[Here goes the title]
Problem statement goes here. But, where does go title?
\end{mythm}

It doesn't look exactly what your example picture looks like, but as the "Sample Problem 3.1" text is bold making the title also bold wouldn't benefit readability.