The simplify/piecewise command can simplify expressions with piecewise functions of one variable. If the expression contains more than one variable use the convert(expr, piecewise, var) calling sequence or the long form `simplify/piecewise`(expr, var).

$A≔\mathrm{convert}\left(\mathrm{abs}\left(x\right)\,\mathrm{piecewise}\right)$

$A≔\left\{\begin{array}{cc}-x& x<0\\ x& 0\le x\end{array}\right.$

$\mathrm{simplify}\left(AA\right)$

$x^2$

$B≔\mathrm{piecewise}\left(x^2-4<0\&comma;-x\&comma;xx\right)$

$B≔\left\{\begin{array}{cc}-x& x^2<4\\ x^2& \mathrm{otherwise}\end{array}\right.$

$\mathrm{simplify}\left(B-\left(\mathrm{piecewise}\left(3<x\&comma;0\&comma;1\right)\right)\right)$

$\left\{\begin{array}{cc}{x}^2-1& x\le \mathrm{-2}\\ -x-1& x<2\\ x^2-1& x\le 3\\ x^2& 3<x\end{array}\right.$

$\mathrm{`simplify/piecewise`}\left({\left(\mathrm{piecewise}\left(0<x\&comma;a\&comma;b\right)\right)}^2\&comma;x\right)$

${\left(\left\{\begin{array}{cc}b& x\le 0\\ a& 0<x\end{array}\right.\right)}^2$