\title	{Symmetry of the plane}
\language{en}
\author	{XIAO Gang}
\email	{xiao@unice.fr}
\format	{html}
\range  {-5..5}
\precision{10000}

\matrix{data=
1,0.0,-1, 2, reflection with respect to the line y=0
-1,0.0,1, 1, reflection with respect to the line x=0
-1,0.0,-1,4, central symmetry with respect to the origin
0,1.1,0,  5, reflection with respect to the line y=x
0,-1.-1,0,4, reflection with respect to the line x+y=0
0,1.-1,0, 7, clockwise rotation of 90 degrees
0,-1.1,0, 6, counter-clockwise rotation of 90 degrees
}
\integer{datacnt=rows(\data)}
\text{ch=shuffle(\datacnt)}
\text{ch=item(1..4,\ch)}
\text{good=item(1,\ch)}
\text{ch=shuffle(\ch)}
\text{A=item(1,\ch)}
\text{B=item(2,\ch)}
\text{C=item(3,\ch)}
\text{D=item(4,\ch)}
\text{aa=item(5,row(\A,\data))}
\text{bb=item(5,row(\B,\data))}
\text{cc=item(5,row(\C,\data))}
\text{dd=item(5,row(\D,\data))}
\text{goodrow=row(\good,\data)}
\text{goodtext=item(5,\goodrow)}
\text{badrow=item(4,\goodrow)}
\text{badtext=item(5,row(\badrow,\data))}
\text{mat=wims(translate . to ; in item(1..3,\goodrow))}

\statement{What is the nature of the plane transformation given by the matrix
\([\mat])&nbsp;?
}

\choice{The reply is}{\goodtext}{\badtext,\aa,\bb,\cc,\dd}

