randRange( 0, 1 ) randRange( 3, 8 ) randRange( 0, SIDES - 1 ) [\$._("Yes"), \$._("No")] SYM ? YES : NO

Is the blue line an axis of symmetry?

init({ range: [ [ -5, 5 ], [ -5, 5 ] ] }); graph.polygon = new RegularPolygon( [ 0, 0 ] , SIDES , 3 ); if ( SYM ){ graph.split = graph.polygon.drawLineOfSymmetry( SIDE ); } else { graph.split = graph.polygon.drawFakeLineOfSymmetry( SIDE ); }
• YES
• NO

Does the blue line split the shape into two parts which look like reflections of each other?

The orange line is one of two parts made by the blue line.

graph.half = graph.polygon.splitPath( graph.split ).graphiePath;

If the blue line were a mirror, what would the orange line's reflection look like?

The pink line is the orange line's reflection.

var temp = []; var i = 0; for( i = 0; i != graph.half.length; i++ ){ temp.push( reflectPoint( graph.split.graphiePath, graph.half[ i ] ) ); } path( temp, { "stroke-width": 5, stroke: KhanUtil.PINK } )

The blue line splits the shape into two equal halves, so it is an axis of symmetry.

The blue line did not split the shape into two equal halves, so it is not an axis of symmetry.