Inline formulas are typeset by TEX and move with the words around them. When the paragraph re-breaks, a formula moves from line to line whole, with TEX’s spacing. Below is the complete example, with its source underneath.
Inline mathematics
The Knuth–Plass algorithm chooses line breaks by minimising the total demerits of a paragraph. Reflow TeX runs it in the browser, not at compile time, so this paragraph fits whatever width the page gives it, while the inline mathematics keeps TEX’s spacing: Euler’s identity, the Cauchy–Schwarz bound, the golden ratio, a binomial coefficient, and a quantified statement. Resize the window and the lines re-break around the formulas.
\section*{Inline mathematics}The Knuth--Plass algorithm chooses line breaks by minimising the total
demerits of a paragraph. Reflow TeX runs it in the browser, not at compile time,
so this paragraph fits whatever width the page gives it, while the inline
mathematics keeps \TeX's spacing: Euler's identity
$e^{i\pi} +1=0$, the Cauchy--Schwarz bound
$\abs{\langle x, y\rangle} \le\norm{x}\,\norm{y}$, the golden ratio
$\varphi=\tfrac{1+\sqrt{5}}{2}$, a binomial coefficient $\binom{n}{k}$, and a
quantified statement $\forall\,\varepsilon > 0\ \exists\,\delta > 0$. Resize
the window and the lines re-break around the formulas.