I've got a very long radical in a display-math environment, so long that the equation spills in the right margin. How can I break that equation over multiple lines, so that it doesn't go into the right margin?
\documentclass[12pt,a4paper]{article}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}
\usepackage{fourier}
\usepackage[left=3cm,right=3cm,top=2.5cm,bottom=2cm]{geometry}
\begin{document}
\[
V_{DABC}=\dfrac{1}{6}\cdot DA \cdot DB \cdot DC \cdot \sqrt{1+2\cdot
\cos \widehat{ADB}\cdot \cos \widehat{BDC}\cdot \cos \widehat{ADC}
-\cos^2 \widehat{ADB} -\cos^2 \widehat{ADC} -\cos^2 \widehat{BDC}}
=\dfrac{2\sqrt{2}}{3}.
\]
\end{document}
\alpha
,\beta
and so on instead of naming angles by points.)^{1/2}
instead of a root? would be easier to split up.